The habitat, double life, citizenship, and forgetfulness of IgA

Immunoglobulin A (IgA) is the main secretory immunoglobulin of mucous membranes and is powerfully induced by the presence of commensal microbes in the intestine. B cells undergo class switch recombination to IgA in the mucosa-associated lymphoid tissues, particularly mesenteric lymph nodes (MLNs) and Peyer's patches, through both T-dependent and T-independent pathways. IgA B cells primed in the mucosa traffic from the intestinal lymphoid structures, initially through the lymphatics and then join the bloodstream, to home back to the intestinal mucosa as IgA-secreting plasma cells. Once induced, anti-bacterial IgA can be extremely long-lived but is replaced if there is induction of additional IgA specificities by other microbes. The mucosal immune system is anatomically separated from the systemic immune system by the MLNs, which act as a firewall to prevent penetration of live intestinal bacteria to systemic sites. Dendritic cells sample intestinal bacteria and induce B cells to switch to IgA. In contrast, intestinal macrophages are adept at killing extracellular bacteria and are able to clear bacteria that have crossed the mucus and epithelial barriers. There is both a continuum between innate and adaptive immune mechanisms and compartmentalization of the mucosal immune system from systemic immunity that function to preserve host microbial mutualism.

Estimating the Size of the Homeless Population in Budapest

Since 1990, the issue of homelessness has become increasingly important in Hungary as a result of economic and structural changes. Various suggestions as to how the problem may be solved have always been preceded by the question "How many homeless people are there?" and there is still no official consensus as to the answer. Counting of the homeless is particularly difficult because of the bias in the initial sampling frame due to two factors that characterise this population: the definition of homelessness, and its 'hidden' nature. David aimed to estimate the size of the homeless population of Budapest by using two non-standard sampling methods: snowball sampling and the capture-recapture method. Her calculations are based on three data sets: one snowball data set and two independent list data sets. These estimators, supported by other statistical data, suggest that in 1999 there were about 8000-10000 homeless people in Budapest.

Meanings of Citizenship: Czech Citizen in a Comparative Perspective

This was an interdisciplinary cross-cultural project which subjected Czech citizens to theoretical analysis and empirical examination. In the first, theoretical, part of the work a typology of post-totalitarian citizenship was proposed containing five types of citizens: responsible democratic, social materialistic, passive asocial, hedonistic consuming, and predatory antisocial. While democratic citizenship stems from preserved civic virtues, the deficient types of citizenship are partially caused by the post-totalitarian syndrome. In the concrete empirical studies of the international context the most significant aspects of citizenship were examined. Czech citizens (students) displayed an encouraging level of political civic culture when they loaded more often than six other national samples on the factor of democratic citizenship (based on a questionnaire and Q-sort by Feierabend, Q-factor analysis), but their level of loyalty and low critical rebelliousness can also be seen as reason for concern. The Czech population provided contrasting results in measures of civility; although chronically complaining about interpersonal relations, they passed relatively well in a series of situational field experiments even in the international comparison (Levine's helping measures. Czech nationalism is primarily "cultural nationalism", which is less favourable for democratic citizenship than the "civic nationalism" of Americans.