AGE-RELATED-CHANGES OF NAIVE AND MEMORY CD4 RAT LYMPHOCYTE SUBSETS INMUCOSAL AND SYSTEMIC LYMPHOID ORGANS

The purpose of this study was to investigate in rats, by double-label immunofluorescence and flow cytometric analysis, the age related chang es in the CD4 subset of gut-associated lymphoid tissues and spleen. We found that the percentage of CD4 + T cells in Peyer's patches (PP) an d spleen (SP) increased during the first 6 weeks after weaning. An age -related decrease of the CD4 subset was observed in SP of aged rats, b ut not in their PP. In all lymphoid tissues studied, an age-related de crease of the Thy-1 + subset was observed from weaning to 2 years of a ge. Analysis of the naive CD4 subset (CD45RC +) showed that in SP this subset increased during the first 9 weeks of age, and declined in age d rats. However, in PP this subset presented a slow decrease from wean ing until 2 years of age. Together with the decrease of the naive subs et, a sharp increase of the memory/activated CD4 + cells (CD45RC - Thy -1 -) was observed in PP, and to a lesser extent in SP. When the matur ation of the CD4 T cells in PP was followed during the first week afte r weaning, we found that an important proportion of this subset change s its phenotype at this time, from recent thymic emigrant (CD45RC - Th y-1 +) to naive T cell (CD45RC + Thy-1 -) and then to activated/memory cell (CD45RC - Thy-1 -). Therefore it appeared that CD4 T cells from PP mature faster than SP CD4 T cells, and they are not subject to the deleterious effect of aging. One surprising point was the different ki netics of the CD4 T cells observed in mesenteric lymph nodes (MLN). No age-related changes were observed in the CD4 subset at this site. Fur thermore, the percentage of the CD45RC + cells did not decrease in age d rats, and in the first 9 weeks of life an increase of this subset wa s observed. (C) 1997 Elsevier Science Ltd.