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Phenotypic and functional analysis of porcine T cells from jejunal/ileal lymphoid tissues

This study compares the quantitative profiles of porcine T and B lymphocytes in the peripheral blood (PB) thymus (T), bone marrow (BM), spleen (S), mesenteric lymph node (MLN), jejunal lamina propria (JLP) and ileal Peyer's patches (IPP), and relates it to the immune maturity/competence in conventionally reared suckling 3- or 4-, and weaned 5-or 8-week-old pigs. Also, distribution patterns of T cell subsets were studied in the small intestinal mucosa of 8-week-old pigs. Based on phenotypic and functional expression of CD+ cell subsets during the postnatal immune ontogeny of the pig, our investigations address basic question about the production rate of these cells within porcine lymphytic tissues tested. Generally, the proportion of T and B cells in PB, S and GALT compartments tested increases with age and reaches the adult values at 8 weeks of life. The number of double positive extrathymic T cells (CD4+ CD8+) also increases in older pigs reflecting the immune maturation. The functional maturity of PBL was expressed as stimulation index which seems to be more relevant when the cells of younger pigs were tested. Phenotypic diversity of jejunal/ileal cytolytic and suppressor T cell subsets in 8-week-old pigs was demonstrated by either avidine-biotin complex (ABC) or peroxidase-antiperoxidase (PAP) immunohistochemical methods. With monoclonal antibodies specific for CD3a membrane antigen used in ABC method we have demonstrated the presence of that epitope on jejunal intraepithelial lymphocytes, lamina propria lymphocytes, and on small amount of T cells between crypts. In ileum were found numerous clusters of CD3a+ T lymphocytes between Peyer’s patch follicles and solitary cells in the follicles. Numerous CD3a+ cells were observed in the apical region of villi, which indicate their possible intraluminal migration. Using polyclonal antibodies specific for S-100 protein (known as a specific marker for human suppressor CD8+ CD11b+ T cells) in PAP method we have investigated the presence of analogous T cell phenotype in swine. The most frequent S-100+ T cells were found in jejunal/ileal lamina propria, particularly between the crypts. However, in the ileum we have observed a specific localization of these cells beneath the epithelial basal membrane of the vill. If s-100 protein binds to porcine CD3a+CD8+CD4- suppressor T cells, then it would be possible by identifying CD3a+ and S-100+ cells in paraffin tissue sections, to establish the distribution of cytolytic CD3a+CD8+CD4- S-100- and suppressor CD3a+CD8+CD4- S-100+ T lymphocytes in the small intestinal mucosa of pigs. This would implicate the patterns and possible result of a local immune reaction to dietary antigens and/or intestinal pathogens, such as E. coli strains used in the model of postweaning colibacillosis.

Immunophenotype; T cells; small intestine; pig

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