DIFFERENCES IN DEVELOPMENT OF LYMPHOCYTE SUBPOPULATIONS FROM GUT-ASSOCIATED LYMPHATIC TISSUE (GALT) OF GERM-FREE AND CONVENTIONAL RATS - EFFECT OF AGING

The aim of the study was to compare the phenotype of lymphocyte subpop ulations of the GALT (gut-associated lymphatic tissue) in germfree (GF ) and conventionally (CV) reared rats, i.e. to analyze the effect of m icrobial colonization on the development of intestinal lymphocyte subs ets. Surface marker characteristics were studied in cell suspensions i solated from Peyer's patches, mesenteric lymph nodes, spleen and the i ntraepithelial lymphocyte compartment of 2- and 12-month old inbred AV N rats. The pattern of T lymphocyte phenotypes in Peyer's patches, mes enteric lymph nodes and spleen determined by FAGS analysis did not rev eal differences between GF and CV rats. In contrast, a 2-month convent ionalization of GF rats led to substantial changes in the composition of intestinal intraepithelial lymphocyte subsets (IELs): increase of C D4(+), CD8 alpha(+), CD8 beta(+), TcR alpha/beta(+) bearing lymphocyte s was observed after colonization of rats with normal microflora Surpr isingly, the relative numbers of lymphocytes bearing TcR gamma/delta() did not change during conventionalization The effect of aging was al so studied and differences in IELs composition of aged (GF) and (CV) r ats were found to be more pronounced: 6,6 % and 30 % of lymphocytes be aring TcR aip were present among IELs in two-month old GF and CV rats, respectively. 30 % of IELs in 2-month old GF rats, 80 % of IEL from 1 2-month old CV rats were found to bear TcR alpha/beta This finding dem onstrates that during conventionalization and aging the TcR alpha/beta bearing population of IELs substantially expands. It suggests that ma inly this lymphocyte subset responds to microflora stimuli and is prob ably involved in the protection of the epithelial cell layer of intest inal mucosa.