SPONTANEOUS PROLIFERATION OF PEYERS PATCH CELLS IN-VITRO

Under normal circumstances most lymphoid cell populations do not exhib it strong proliferative reactions in culture unless provoked by antige n or mitogen. The autologous mixed lymphocyte reaction (AMLR) mediated by adult T cells is a relatively weak proliferative response that occ urs in the absence of known heterologous stimuli. In this investigatio n we demonstrate that Peyer's patch (PP) cells possess an inherent cap acity to commence dividing in vitro and to display an exceptionally vi gorous AMLR. The magnitude and kinetics of this spontaneous proliferat ion resemble that of a secondary response to a strong mucosal immunoge n such as reovirus type 1/Lang. Analysis of the cellular components of the PP cultures implicates CD4+CD8- T cells as the major responding p opulation and dendritic cells (DC) as stimulators. Mixing experiments indicate that spleen contains a cell population which can stimulate PP T cells, albeit to a lesser extent than PP cells. Similarly, splenic T cells have a reduced but significant capacity to respond to PP DC, i n comparison to PP T cells. These differences suggest the possibility that there may be a decreasing gradient of antigenicity between the gu t and the spleen which is reflected in the spontaneous activity of PP versus splenic T cells in vitro. We propose that PP cells are in fact responding in vitro to heterologous antigens derived from food, enteri c microbes and other environmental sources. This notion is supported b y the observation that PP cells from antigen-minimized germ-free mice fail to proliferate spontaneously in culture.