Selective expression of beta 7 integrin on lymphocytes undergoing apoptosis in lymphoid tissues

It has been previously shown that the beta 7 chain of integrin forms heterodimers with the alpha 4 or alpha E chain, which plays essential roles in lymphocyte homing to mucosal lymphoid tissues. The aim of this study was to re-evaluate the possible role of the beta 7 integrin other than lymphocyte homing. We prepared spleen and lymph node lymphocytes from biopsied specimens from macaque monkeys and examined for the reactivity with a monoclonal antibody specific for the beta 7 chain. As a result, a minor population of the lymphocytes with a smaller size, which were in the early stage of apoptosis, was found to express a higher level of the beta 7 integrin than a majority of the lymphocytes with a normal size. Interestingly, the apoptotic lymphocytes expressed neither alpha 4 nor alpha E chains, suggesting that the beta 7 chain on these cells may be associated with an undefined alpha chain. These findings indicate that in the lymphoid tissues the shrunken lymphocytes undergoing apoptosis selectively express a unique beta 7 integrin.