EXPRESSION OF MUCOSAL HOMING RECEPTOR ALPHA-4-BETA-7 BY CIRCULATING CD4(+) CELLS WITH MEMORY FOR INTESTINAL ROTAVIRUS

The integrin alpha 4 beta 7 mediates lymphocyte binding to mucosal add ressin cell adhesion molecule-1, and its expression defines lymphocyte s capable of trafficking through the intestines and the intestinal lym phoid tissues, We examined the ability of discrete alpha 4 beta 7(hi) and alpha 4 beta 7(-) subsets of circulating memory phenotype (CD45RA( -)) CD4(+) T cells to proliferate in response to rotavirus, a ubiquito us intestinal pathogen. alpha 14 beta 7(hi) memory (CD45RA(-)) CD4(+) T cells displayed much greater reactivity to rotavirus than alpha 4 be ta 7(-) memory or naive (CD45RA(+)) CD4(+) T cells, In contrast, alpha 4 beta 7(-) memory cells were the predominant population responsive t o mumps antigen after intramuscular vaccination. Our results are consi stent with the conclusion that natural rotavirus infection, an enteric pathogen, results in a specific circulating memory CD4(+) response th at is largely limited to the gut-homing alpha 3 beta 7(+) subpopulatio n, This phenotype is not shared with memory cells elicited by intramus cular immunization (shown here) or by skin contact allergens, The resu lts support the hypothesis that gut trafficking memory CD4(+) T cells comprise cellular memory for intestinal antigens and suggest that regu lated expression of alpha 4 beta 7 helps target and segregate intestin al versus systemic immune response.