DENDRITIC CELL HETEROGENEITY IN-VIVO - 2 FUNCTIONALLY DIFFERENT DENDRITIC CELL-POPULATIONS IN RAT INTESTINAL LYMPH CAN BE DISTINGUISHED BY CD4 EXPRESSION

DC derived from rat pseudo-afferent lymph (L-DC) vary in CD4, CD11b/c, Thy1, and OX41 expression CD4 and OX41 are expressed by the same subp opulation (50-60%) of L-DC. CD4(+)/OX41(+) L-DC express short fine pro cesses and low nonspecific esterase, whereas CD4(-) DC/OX41(-) express long pseudopodia, high nonspecific esterase, and many cytoplasmic inc lusions. These differences are stable in culture. Both populations exp ress similar amounts of MHC class II, ICAM-1, CD11b/c and OX62, Most C D4(-)/OX41(-) L-DC are strongly positive for B7, but CD4(+) L-DC expre ss less B7, and some may be negative. Both populations express invaria nt chain, but both the absolute numbers and levels of expression were higher for CD4(-) DC. Surprisingly, CD4(+) L-DC are more potent APC th an CD4(-) cells in MLRs, for sensitized T cells in vitro and for naive T cells in vivo. Cultured CD4(+)/OX41(+) DC can still process and pre sent native Ag. Cultured CD4(-)/OX41(-) cells cannot present native Ag but can stimulate strong MLRs, CD4(-) DC invariant chain expression d ecreases in culture, whereas expression by CD4(+) DC is stable for 48 h, CD4(+) and CD4(-) L-DC have similar turnover times in vivo, suggest ing that one population is not the precursor of the other. Thus, two s eparate DC populations that differ functionally and phenotypically mig rate from intestine to mesenteric nodes. This may reflect distinct DC lineages or differentiation modulated by different microenvironmental stimuli.