THE MOLECULAR INTERACTION BETWEEN TYPE II DIABETES AND ALZHEIMER’S DISEASE THROUGH CROSS-SEEDING OF PROTEIN MISFOLDING

With the population of the world aging, the prominence of diseases such as Type II Diabetes (T2D) and Alzheimer’s disease (AD) are on the rise. In addition, patients with T2D have an increased risk of developing AD compared to age-matched individuals, and the number of AD patients with T2D is higher than among aged-matched non-AD patients. AD is a chronic and progressive dementia characterized by amyloid-beta (Aβ) plaques, neurofibrillary tangles (NFTs), neuronal loss, brain inflammation, and cognitive impairment. T2D involves the dysfunctional use of pancreatic insulin by the body resulting in insulin resistance, hyperglycemia, hyperinsulinemia, pancreatic beta cell (β-cell) death, and other complications. T2D and AD are considered protein misfolding disorders (PMDs). PMDs are characterized by the presence of misfolded protein aggregates, such as in T2D pancreas (islet amyloid polypeptide - IAPP) and in AD brain (amyloid– Aβ) of affected individuals. The misfolding and accumulation of these proteins follows a seeding-nucleation model where misfolded soluble oligomers act as nuclei to propagate misfolding by recruiting other native proteins. Cross-seeding occurs when oligomers composed by one protein seed the aggregation of a different protein. Our hypothesis is that the pathological interactions between T2D and AD may in part occur through cross-seeding of protein misfolding. To test this hypothesis, we examined how each respective aggregate (Aβ or IAPP) affects the disparate disease pathology through in vitro and in vivo studies. Assaying Aβ aggregates influence on T2D pathology, IAPP+/+/APPSwe+/- double transgenic (DTg) mice exhibited exacerbated T2D-like pathology as seen in elevated hyperglycemia compared to controls; in addition, IAPP levels in the pancreas are highest compared to controls. Moreover, IAPP+/+/APPSwe+/- animals demonstrate abundant plaque formation and greater plaque density in cortical and hippocampal areas in comparison to controls. Indeed, IAPP+/+/APPSwe+/- exhibit a colocalization of both misfolded proteins in cerebral plaques suggesting IAPP may directly interact with Aβ and aggravate AD pathology. In conclusion, these studies suggest that cross-seeding between IAPP and Aβ may occur, and that these protein aggregates exacerbate and accelerate disease pathology, respectively. Further mechanistic studies are necessary to determine how these two proteins interact and aggravate both pancreatic and brain pathologies.

Hypertension and cognitive decline among patients of Alzheimer's disease

Objective. The main aim of our study is to assess the effect of hypertension on the decline in cognitive impairment among Alzheimer’s patients. Methods. We analyzed the data of AD patients enrolled in Baylor ADMDC in a prospective study design. We divided AD patients into two groups based on the definition of hypertension. We described a decline in cognitive impairment as a change of 5 points in mini-mental state examination score (MMSE) from the baseline visit. Results. Independent of covariates, AD patients with hypertension did not exhibit a significant decline in cognitive impairment after adjustment of covariates, age, race and education (Hazard Ratio (HR) = 1.07, p value 0.58, 95% confidence interval 0.84-1.39) than AD patients without hypertension. In addition, AD patients with hypertension did not experience decline in cognitive impairment sooner than AD patients without hypertension. (P value 0.83). Conclusions . Hypertension is not associated with cognitive impairment over time among patients with Alzheimer’s disease enrolled in Baylor ADMDC after other potential confounders were taken into account. These findings should not be interpreted as a basis for discouraging appropriate medical treatment of hypertension in AD patients. Greater efforts should be made to improve the recognition of hypertension as a modifiable risk factor for decline in cognitive impairment in AD population. ^

CONFORMATIONAL CHANGES IN THE EXTRACELLULAR DOMAIN OF GLUTAMATE RECEPTORS

The family of membrane protein called glutamate receptors play an important role in the central nervous system in mediating signaling between neurons. Glutamate receptors are involved in the elaborate game that nerve cells play with each other in order to control movement, memory, and learning. Neurons achieve this communication by rapidly converting electrical signals into chemical signals and then converting them back into electrical signals. To propagate an electrical impulse, neurons in the brain launch bursts of neurotransmitter molecules like glutamate at the junction between neurons, called the synapse. Glutamate receptors are found lodged in the membranes of the post-synaptic neuron. They receive the burst of neurotransmitters and respond by fielding the neurotransmitters and opening ion channels. Glutamate receptors have been implicated in a number of neuropathologies like ischemia, stroke and amyotrophic lateral sclerosis. Specifically, the NMDA subtype of glutamate receptors has been linked to the onset of Alzheimer’s disease and the subsequent degeneration of neuronal cells. While crystal structures of AMPA and kainate subtypes of glutamate receptors have provided valuable information regarding the assembly and mechanism of activation; little is known about the NMDA receptors. Even the basic question of receptor assembly still remains unanswered. Therefore, to gain a clear understanding of how the receptors are assembled and how agonist binding gets translated to channel opening, I have used a technique called Luminescence Resonance Energy Transfer (LRET). LRET offers the unique advantage of tracking large scale conformational changes associated with receptor activation and desensitization. In this dissertation, LRET, in combination with biochemical and electrophysiological studies, were performed on the NMDA receptors to draw a correlation between structure and function. NMDA receptor subtypes GluN1 and GluN2A were modified such that fluorophores could be introduced at specific sites to determine their pattern of assembly. The results indicated that the GluN1 subunits assembled across each other in a diagonal manner to form a functional receptor. Once the subunit arrangement was established, this was used as a model to further examine the mechanism of activation in this subtype of glutamate receptor. Using LRET, the correlation between cleft closure and activation was tested for both the GluN1 and GluN2A subunit of the NMDA receptor in response to agonists of varying efficacies. These investigations revealed that cleft closure plays a major role in the mechanism of activation in the NMDA receptor, similar to the AMPA and kainate subtypes. Therefore, suggesting that the mechanism of activation is conserved across the different subtypes of glutamate receptors.

Association between cardiorespiratory fitness and Alzheimer's mortality: A prospective cohort study

Context. Alzheimer’s disease is a major source of morbidity and mortality in aging societies. Preventive measures, such as increasing cardiorespiratory fitness, to reduce the risk of Alzheimer’s disease mortality have not been sufficiently examined.^ Objective. To examine the association between levels of cardiorespiratory fitness and Alzheimer’s disease mortality.^ Design, Setting, and Patients. A prospective cohort study of 53,911 men and 18,876 women (mean age, 51.4 [SD, 10.0] years; range 20-88) enrolled in the Cooper Center Longitudinal Study who completed a baseline health examination during 1970-2006. The primary exposure, cardiorespiratory fitness, was assessed via a maximal exercise test. Fitness was categorized according to age- and sex-specific tertiles based on the participants’ distribution of maximal treadmill exercise test duration, in metabolic equivalent tasks (METs). The main outcome measure was Alzheimer’s disease mortality, defined as the underlying or contributing cause of death using the National Death Index and death certificates through December 31, 2006.^ Results. There were 175 Alzheimer’s disease deaths during a mean follow up of 37 years and 1,309,170 person-years of exposure. Women in the high fitness category had a 70% reduction in risk of Alzheimer’s mortality compared to women in the low fitness category (HR=0.3; 95% CI, 0.1-0.8; P=.02), while adjusting for potential confounders. Similarly, women in the moderate fitness category had a 70% reduction in risk for AD mortality compared to women in the low fit category (HR=0.3; 95% CI, 0.1-0.7; P=.005). Among men, the relationship between fitness level and AD mortality risk was examined but none were of statistical significance. The adjusted comparison of men in the high fitness category to low fit men yielded an HR of 0.9 (95% CI, 0.6-1.5; P=.79), while moderately fit men compared to low fit men yielded an HR of 1.3 (95% CI, 0.9-1.9; P=.21).^ Conclusions. Higher levels of cardiorespiratory fitness were associated with decreased risk of AD mortality, in women. No statistically significant association was found among men. Physical fitness may be an important protective factor against Alzheimer’s disease death in women, further supporting its clinical and public health values.^

{\it In vivo\/} magnetic resonance studies of experimental liver disease: Carbon tetrachloride hepatotoxicity and alcohol-induced fatty liver in rat

Magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) were used to non-invasively determine if cirrhosis induced by carbon tetrachloride (CCl$\sb4$) and phospholipase-D (PLD) could be distinguished from fatty infiltration in rat. MRS localization and water suppression methods were developed, implemented and evaluated in terms of their application to in vivo proton NMR studies of experimental liver disease. MRS studies were also performed to quantitate fatty infiltration resulting from carbon tetrachloride (CCl$\sb4$) or alcohol (ethanol) administration and the MRS results were confirmed using biochemical total lipid analysis and histology. $\rm T\sb1$ weighted MR images acquired weekly, 48 hours post administration, demonstrated only a slight increase in overall liver intensity with CCl$\sb4$ or alcohol administration, which is consistent with previously reported results. The MR images were able to detect nodules resulting from CCl$\sb4$+PLD induced cirrhosis as hypointense regions, also consistent with previous reports. Localized in vivo water and lipid proton $\rm T\sb1$ relaxation time measurements were performed and demonstrated no statistically significant trends for either agent. In vivo proton spectra were also acquired using stimulated echo techniques to quantitatively follow the changes in liver lipid content. The changes in liver lipid content observed using MRS were verified by total lipid analysis using the Folch technique and histology. The in vivo $\rm T\sb1$ and lipid quantification data str inconsistent with the previous hypothesis that the changes in $\rm T\sb1$ weighted images were the result of increased "free" water content and, therefore, increased water $\rm T\sb1$ relaxation times. These data indicate that the long term changes are more likely the result of changes in lipid content. The data are also shown to agree with the accepted hypothesis that the time course and mechanism of fatty infiltration are different for CCl$\sb4$ and alcohol. The hypothesis that the lipids resulting from either protocol are from the same lipid fraction(s), presumably triglycerides, is also supported. And lastly, on the basis of MR images and quantitative MRS lipid information, it was shown that cirrhosis could be distinguished from fatty infiltration. ^

IMMUNOGLOBULINS IN PERIODONTAL DISEASE

Periodontal disease is the major cause of tooth loss in man. The initial histological picture of the inflamed gingiva is characteristic of local inflammatory reaction involving polymorphonuclear leukocytes, vasculitis and localized tissue loss. Subsequent clinical stages of periodontal disease (mild gingivitis) show histological evidence of the involvement of the immune response with initial accumulation of macrophages, and lymphocytes devoid of surface staining immunoglobulins (presumably T cells). As the disease progresses, a predominance of surface and cytoplasmic staining lymphocytes and plasma cells are seen (severe gingivitis and periodontitis). Whether the occurrence of the immunoglobulin positive lymphocytes and the concurrent loss of collagen and resorption of alveolar bone seen in periodontitis is indicative of a direct cause and effect relationship has been a controversy.^ The majority of investigations in the periodontal field have involved the use of peripheral blood lymphocytes or serum. Blastogenic responses of peripheral blood lymphocytes and serum antibody titers from periodontal patients to a variety of oral bacteria have not shown any correlation between response and the severity of disease. The need to study the local immune response in inflamed gingiva is apparent. Since there are no baseline studies on the functional capabilities of the lymphoid cells present in gingiva from periodontitis patients, an in depth study involving the role of the immunoglobulin positive lymphocytes was investigated.^ Inflamed gingiva from four clinically defined periodontal disease states (mild gingivitis, severe gingivitis, periodontitis and severe periodontitis) were placed in gingival organ cultures. Class specific immunoglobulins were quantitated in gingival organ culture supernatants using an indirect sandwich technique. A significant difference in mean levels of IgA and IgG was seen between mild gingivitis and periodontitis (P < .00l, P = .001), as well as in IgG levels between periodontitis and severe periodontitis (P = .001). The predominance of IgG in gingival organ culture supernatants and the statistically significant findings that the overall mean levels of IgG between mild gingivitis and periodontitis (P = .014) and between severe periodontitis and periodontitis (P = .001) suggested a possible indicator of periodontal disease. The presence of IgG in gingival organ culture supernatants was shown to be a product of actively secreting plasma cells. The incorporation of radiolabelled amino acids into IgG was noted over a seven-day period with a peak response at day 4-5. The inhibition of IgG synthesis by cyclohexamide confirmed the contention that IgG was a product of de novo synthesis and not serum derived.^ The specificity of immunoglobulins derived from gingival organ cultures were studied using a whole bacterial agglutination test. Oral bacteria frequently cultured from periodontal patients were assessed for their ability to be agglutinated by gingival organ culture supernatants. A positive correlation of antibody titer and severity of disease was seen with five strains of Actinomyces viscosus, two of Actinomyces naeslundii and one Actinomyces israelii. The agglutination of bacteria was shown to be due to the specific interaction of immunoglobulin and cell-wall antigen. ^

Evaluation of Mycobacterium avium complex lung disease in women

Mycobacterium avium complex (MAC) is a ubiquitous organism responsible for most pulmonary and disseminated disease caused by non-tuberculosis (NTM) mycobacteria. Though MAC lung disease without predisposing factors is uncommon, in recent years it has been increasingly described in middle-aged and elderly women. Recognition and correct diagnosis, is often delayed due to the indolent nature of the disease. It is unclear if these women have significant clinical disease as or if their airways are simply colonized by the bacterium. This study describes the clinical presentation, identifies risk factors, and describes the clinical significance of MAC lung disease in HIV-negative women aged 50 or greater. ^ A hybrid study design utilizing both cross-sectional and case-control methodologies was used. A comparison population was selected from previously identified tuberculosis suspects found throughout Harris County. The study population had at least one acid fast bacillus pulmonary culture performed between 1/1/1998 and 12/31/2000 from a pulmonary source. Clinical presentation and symptoms were analyzed using a cross-sectional design. Past medical history and other risk factors were evaluated using a traditional case-control study design. Differences in categorical variables were estimated with the Chi Square or Fisher's Exact test as appropriate. Odds ratios and 95% confidence intervals were utilized to evaluate associations. Multivariate logistic regression was used to identify predictive factors for MAC. All statistical tests were two-sided and P-values <0.05 were considered statistically significant. ^ Culture confirmed MAC pulmonary cases were more likely to be white, have bronchiectasis, scoliosis, evidence of cavitation and pleural changes on chest radiography and granulomas on histopathologic examination than women whose pulmonary cultures were AFB negative. After controlling for selected risk factors, white race continued to be significantly associated with MAC lung disease (OR = 4.6, 95% CI = 2.3, 9.2). In addition, asthma history, smoking history and alcohol use were less likely to be evident among MAC cases in a multivariate analysis. Right upper and right middle lobe disease was further noted among clinically significant cases. Based on population data, MAC lung disease appears to represent a significant clinical syndrome in HIV-negative women thus supporting the theory of the Lady Windermere Syndrome. ^

Anti-glomerular basement membrane glomerulonephritis: Characterization of an epitope, antibody response, and the potential role of IL-4Ralpha in disease progression

Anti-Glomerular Basement Membrane Glomerulonephritis (anti-GBM GM) is one of the earliest described autoimmune disorders. Patients present with proteinuria, anti-GBM antibodies, and renal failure. Studies have implicated a T Helper 1 (TH1) response in disease induction and a T Helper 2 (TH2) response for disease progression. A 13 amino acid long peptide sequence spanning residues 28 through 40 [pCol(28–40)] of the Collagen IV α3 non-collagen domain (Col IV α3 NCD) is immunogenic and induces anti-GBM GN. In order to fully understand disease initiation, this peptide was further characterized. Peptides were created containing one amino acid substitution for the entire length of pCol(28–40) and induction of anti-GBM GN was monitored. When residues 31, 33, or 34 contained the substitution, anti-GBM GN was unable to be induced. Thus, residues 31, 33, and 34 of pCol(28–40) are required for induction of anti-GBM. Glomerular injury is observed as early as 14 days post anti-GBM GN induction. However, the presence of anti-GBM antibodies is not observed until 20 days post immunization. An enlarged lymph node adjacent to the diseased kidney exhibits B cell activation after renal injury and produces antibodies toward GBM. Thus, anti-GBM antibodies are a consequence of the initial renal injury. Differences between disease susceptible and disease resistant rat strains exist in the expression of IL-4Rα, a major player in the TH2 response. IL-4Rα signaling is regulated by soluble IL-4Rα (sIL-4Rα). Low expression levels of sIL-4Rα result in the stabilization of IL-4 binding, while elevated expression sequesters IL-4. Quantitative PCR experiments noted low siL-4Rα expression levels in disease susceptible rats. Induction of an immune response toward sIL-4Rα in this strain was responsible for delayed disease progression in 15 out of the 17 experimental animals. Antibody transfer and in vivo biological activity experiments confirmed that delayed disease development was due to anti-sIL-4Rα antibodies. Together these experiments indicate that a T-cell epitope is required for activation of a TH1 autoimmune response and anti-GBM antibodies are a consequence of renal injury. More importantly, a role for IL-4Rα signaling is implicated in the progression of anti-GBM GN. ^

SERIOUS MORBIDITY DUE TO ACUTE RESPIRATORY DISEASE ASSOCIATED WITH EPIDEMIC INFLUENZA

Current measures of the health impact of epidemic influenza are focused on analyses of death certificate data which may underestimate the true health effect. Previous investigations of influenza-related morbidity have either lacked virologic confirmation of influenza activity in the community or were not population-based. Community virologic surveillance in Houston has demonstrated that influenza viruses have produced epidemics each year since 1974. This study examined the relation of hospitalized for Acute Respiratory Disease (ARD) to the occurrence of influenza epidemics. Considering only Harris County residents, a total of 13,297 ARD hospital discharge records from hospitals representing 48.4% of Harris County hospital beds were compiled for the period July 1978 through June 1981. Variables collected from each discharge included: age, sex, race, dates of admission and discharge, length of stay, discharge disposition and a maximum of five diagnoses. This three year period included epidemics caused by Influenza A/Brazil (H1N1), Influenza B/Singapore, Influenza A/England (H1N1) and Influenza A/Bangkok (H3N2).^ Correlations of both ARD and pneumonia or influenza hospitalizations with indices of community morbidity (specifically, the weekly frequency of virologically-confirmed influenza virus infections) are consistently strong and suggest that hospitalization data reflect the pattern of influenza activity derived from virologic surveillance.^ While 65 percent of the epidemic period hospital deaths occurred in patients who were 65 years of age or older, fewer than 25 percent of epidemic period ARD hospitalizations occurred in persons of that age group. Over 97 percent of epidemic period hospital deaths were accompanied by a chronic underlying illness, however, 45 percent of ARD hospitalizations during epidemics had no mention of underlying illness. Over 2500 persons, approximately 35 percent of all persons hospitalized during the three epidemics, would have been excluded in an analysis for high risk candidates for influenza prophylaxis.^ These results suggest that examination of hospitalizations for ARD may better define the population-at-risk for serious morbidity associated with epidemic influenza. ^

Bayesian and survival model for tumor relapse status and disease-specific survival, with applications to breast cancer

Breast cancer is the most common non-skin cancer and the second leading cause of cancer-related death in women in the United States. Studies on ipsilateral breast tumor relapse (IBTR) status and disease-specific survival will help guide clinic treatment and predict patient prognosis.^ After breast conservation therapy, patients with breast cancer may experience breast tumor relapse. This relapse is classified into two distinct types: true local recurrence (TR) and new ipsilateral primary tumor (NP). However, the methods used to classify the relapse types are imperfect and are prone to misclassification. In addition, some observed survival data (e.g., time to relapse and time from relapse to death)are strongly correlated with relapse types. The first part of this dissertation presents a Bayesian approach to (1) modeling the potentially misclassified relapse status and the correlated survival information, (2) estimating the sensitivity and specificity of the diagnostic methods, and (3) quantify the covariate effects on event probabilities. A shared frailty was used to account for the within-subject correlation between survival times. The inference was conducted using a Bayesian framework via Markov Chain Monte Carlo simulation implemented in softwareWinBUGS. Simulation was used to validate the Bayesian method and assess its frequentist properties. The new model has two important innovations: (1) it utilizes the additional survival times correlated with the relapse status to improve the parameter estimation, and (2) it provides tools to address the correlation between the two diagnostic methods conditional to the true relapse types.^ Prediction of patients at highest risk for IBTR after local excision of ductal carcinoma in situ (DCIS) remains a clinical concern. The goals of the second part of this dissertation were to evaluate a published nomogram from Memorial Sloan-Kettering Cancer Center, to determine the risk of IBTR in patients with DCIS treated with local excision, and to determine whether there is a subset of patients at low risk of IBTR. Patients who had undergone local excision from 1990 through 2007 at MD Anderson Cancer Center with a final diagnosis of DCIS (n=794) were included in this part. Clinicopathologic factors and the performance of the Memorial Sloan-Kettering Cancer Center nomogram for prediction of IBTR were assessed for 734 patients with complete data. Nomogram for prediction of 5- and 10-year IBTR probabilities were found to demonstrate imperfect calibration and discrimination, with an area under the receiver operating characteristic curve of .63 and a concordance index of .63. In conclusion, predictive models for IBTR in DCIS patients treated with local excision are imperfect. Our current ability to accurately predict recurrence based on clinical parameters is limited.^ The American Joint Committee on Cancer (AJCC) staging of breast cancer is widely used to determine prognosis, yet survival within each AJCC stage shows wide variation and remains unpredictable. For the third part of this dissertation, biologic markers were hypothesized to be responsible for some of this variation, and the addition of biologic markers to current AJCC staging were examined for possibly provide improved prognostication. The initial cohort included patients treated with surgery as first intervention at MDACC from 1997 to 2006. Cox proportional hazards models were used to create prognostic scoring systems. AJCC pathologic staging parameters and biologic tumor markers were investigated to devise the scoring systems. Surveillance Epidemiology and End Results (SEER) data was used as the external cohort to validate the scoring systems. Binary indicators for pathologic stage (PS), estrogen receptor status (E), and tumor grade (G) were summed to create PS+EG scoring systems devised to predict 5-year patient outcomes. These scoring systems facilitated separation of the study population into more refined subgroups than the current AJCC staging system. The ability of the PS+EG score to stratify outcomes was confirmed in both internal and external validation cohorts. The current study proposes and validates a new staging system by incorporating tumor grade and ER status into current AJCC staging. We recommend that biologic markers be incorporating into revised versions of the AJCC staging system for patients receiving surgery as the first intervention.^ Chapter 1 focuses on developing a Bayesian method to solve misclassified relapse status and application to breast cancer data. Chapter 2 focuses on evaluation of a breast cancer nomogram for predicting risk of IBTR in patients with DCIS after local excision gives the statement of the problem in the clinical research. Chapter 3 focuses on validation of a novel staging system for disease-specific survival in patients with breast cancer treated with surgery as the first intervention. ^

IMMUNOLOGICAL MECHANISMS OF EXTRACORPOREAL PHOTOPHERESIS IN CUTANEOUS T CELL LYMPHOMA AND GRAFT VERSUS HOST DISEASE

IMMUNOLOGICAL MECHANISMS OF EXTRACORPOREAL PHOTOPHERESIS IN CUTANEOUS T CELL LYMPHOMA AND GRAFT VERSUS HOST DISEASE Publication No.___________ Lisa Harn-Ging Shiue, B.S. Supervisory Professor: Madeleine Duvic, M.D. Extracorporeal photopheresis (ECP) is an effective, low-risk immunomodulating therapy for leukemic cutaneous T cell lymphoma (L-CTCL) and graft versus host disease (GVHD), but whether the mechanism(s) of action in these two diseases is (are) identical or different is unclear. To determine the effects of ECP in vivo, we studied regulatory T cells (T-regs), cytotoxic T lymphocytes (CTLs), and dendritic cells (DCs) by immunofluorescence flow cytometry in 18 L-CTCL and 11 GVHD patients before and after ECP at Day 2, 1 month, 3 months, and 6 months. In this study, ECP was effective in 12/18 L-CTCL patients with a 66.7% overall response rate (ORR) and 6/11 GVHD patients with a 54.5% ORR. Prior to ECP, the percentages of CD4+Foxp3+ T cells in 9 L-CTCL patients were either lower (L-CTCL-Low, n=2) or higher (L-CTCL-High, n=7) than normal. Five of the 7 GVHD patients had high percentages of CD4+Foxp3+ T cells (GVHD-High). Six of 7 L-CTCL-High patients had >80% CD4+Foxp3+ T cells which were correlated with tumor cells, and were responders. Both L-CTCL-High and GVHD-High patients had decreased percentages of CD4+Foxp3+ and CD4+Foxp3+CD25- T cells after 3 months of treatment. CD4+Foxp3+CD25+ T cells increased in GVHD-High patients but decreased in L-CTCL-High patients after 3 months of ECP. In addition, numbers of CTLs were abnormal. We confirmed that numbers of CTLs were low in L-CTCL patients, but high in GVHD patients prior to ECP. After ECP, CTLs increased after 1 month in 4/6 L-CTCL patients whereas CTLs decreased after 6 months in 3/3 GVHD patients. Myeloid (mDCs) and plasmacytoid DCs (pDCs) were also low at baseline in L-CTCL and GVHD patients confirming the DC defect. After 6 months of ECP, numbers and percentages of mDCs and pDCs increased in L-CTCL and GVHD. MDCs were favorably increased in 8/12 L-CTCL responders whereas pDCs were favorably increased in GVHD patients. These data suggest that ECP is favorably modulating the DC subsets. In L-CTCL patients, the mDCs may orchestrate Th1 cell responses to overcome immune suppression and facilitate disease regression. However, in GVHD patients, ECP is favorably down-regulating the immune system and may be facilitating immune tolerance to auto-or allo-antigens. In both L-CTCL and GVHD patients, DCs are modulated, but the T cell responses orchestrated by the DCs are different, suggesting that ECP modulates depending on the immune milieu. _______________