Recent thymic emigrants (CD4+) continuously migrate through lymphoid organs: within the tissue they alter surface molecule expression.

T-cell progenitors migrate from bone marrow (BM) into the thymus. After maturation they are released as recent thymic emigrants (RTE) into the periphery ensuring the diversification of the T-cell repertoire. Both the kinetics with which RTE migrate through the periphery and the surface molecules they express are still unclear. In 1- and 18-month-old Lewis rats CD4+ RTE were identified in blood, spleen, lymph node, and thoracic duct lymph by flow cytometry (CD45RC- and CD90+), were differentiated from CD4+ naive (CD45RC+) and memory T cells (CD45RC-CD90-), and were characterized regarding the expression of surface molecules. Both in 1- and 18-month-old animals the percentage of RTE among the CD4+ population in blood was comparable to that in all other compartments. Surprisingly, RTE expressed alpha4-integrin, LFA-1, and interleukin (IL)-2 receptor at a significantly higher level than naive T cells and more comparable to memory T cells. Within lymphoid tissues RTE, naive, and memory T cells significantly upregulated the expression of CD44 and ICAM-1, and downregulated the expression of L-selectin. These changes were reversed before the cells re-entered the blood. Thus, our data indicate that CD4+ RTE travel through the periphery of young and old rats like mature T cells, continuously modulating their surface molecule expression.

[Mental health policies and changes in emergency service demand]. / Políticas de saúde mental e mudanças na demanda de serviços de emergência.

OBJECTIVE: To verify the modifications observed in a school hospital psychiatric emergency unit in Ribeirão Preto - SP, Brazil (EP-RP), due to alterations in the mental health policies implemented in this region. METHODS: Data about attendances was collected from university hospital files of the EP-RP, from 1988 to 1997. The following variables were studied: sex, age, origin and main diagnosis. Data about changes in mental health policies of the region was obtained from documents of the city and state departments of health. RESULTS: The yearly increase in the number of attendances followed the progressive involvement of EP-RP with the mental health service network, as the number of patients who looked for the service in 1995 was 2.3 times greater than in 1988. During this period, attendance at the EP-RP gave support to the modifications in the mental health policies in this region, resulting in a reduction of 654 psychiatry beds. In 1996 and 1997, a reduction of about 20% was observed in the total of attendance, as compared to 1995, result from an increase in the attendance capacity and number of the extra-hospital services. Since 1990, the EP-RP started to attend a higher proportion of older, male patients, with drug dependency and psychotic disorders and a lower proportion of non-psychotic patients. CONCLUSIONS: The changes observed in the EP-RP are related to modifications in the Ribeirão Preto region mental health policies, like the psychiatric beds control, installed in 1990, the reduction of psychiatric beds after 1993, and the creation and/or amplification of extra-hospital services, in 1995.

CD4+ T cells of both the naive and the memory phenotype enter rat lymph nodes and Peyer's patches via high endothelial venules: within the tissue their migratory behavior differs.

It is thought that naive T cells predominantly enter lymphoid organs such as lymph nodes (LN) and Peyer's patches (PP) via high endothelial venules (HEV), whereas memory T cells migrate mainly into non-lymphoid organs. However, direct evidence for the existence of these distinct migration pathways in vivo is incomplete, and nothing is known about their migration through the different compartments of lymphoid organs. Such knowledge would be of considerable interest for understanding T cell memory in vivo. In the present study we separated naive and memory CD4+ T cells from the rat thoracic duct according to the expression of the high and low molecular weight isoforms of CD45R, respectively. At various time points after injection into congenic animals, these cells were identified by quantitative immunohistology in HEV, and T and B cell areas of different LN and PP. Three major findings emerged. First, both naive and memory CD4+ T cells enter lymphoid organs via the HEV in comparable numbers. Second, naive and memory CD4+ T cells migrate into the B cell area, although in small numbers and continuously enter established germinal centers (GC) with a bias for memory CD4+ T cells. Third, memory CD4+ T cells migrate faster through the T cell area of lymphoid organs than naive CD4+ T cells. Thus, our study shows that memory CD4+ T cells are not excluded from the HEV route. In addition, "memory" might depend in part on the ability of T cells to specifically enter the B cell area and GC and to screen large quantities of lymphoid tissues in a short time.