Cognate interaction between human lymphocytes and eosinophils is mediated by beta 2-integrins and very late antigen-4

Here the cognate interactions between human eosinophils and lymphocytes are studied. These interactions were measured in a double-colored FACS analysis by applying fluorescent red eosinophils (stained with hydroethidine, 40 mumol/L) and fluorescent green lymphocytes (stained with sulfidofluorescein diacetate, 100 mumol/L) in a ratio of 1:3. When normal eosinophils were mixed with a total lymphocyte preparation in stirred suspensions (37 degrees C), no physical interaction was present between both cell types. However, the addition of phytohemagglutinin and PMA resulted in a clear aggregation response between both cell types (up to 30% of the eosinophils interacted with lymphocytes after 15 minutes). CD8(+)- and CD4(+)-positive T cells contributed equally to the heterotypic aggregation response. It is interesting that when lymphocytes were pretreated with phytohemagglutinin or eosinophils with phorbol myristate acetate and subsequently washed, the cells still interacted with unstimulated counterparts. The heterotypic interaction between lymphocytes and eosinophils is blocked by monoclonal antibodies directed against the beta-chain of the beta 2-integrins (CLB LFA1/1; CD18) and the alpha-chain of very late antigen-4 (VLA-4) (HP2/1; CD49d), indicating that both the beta 2-integrins and VLA-4 contributed to this heterotypic interaction. When eosinophils bound to PHA-treated lymphocytes, the cells exhibited an activated phenotype that was characterized by an enhanced expression of CD66b and CD11b. The cells interacted with each other provided that an intact cellular metabolism was present--that is, no interaction was seen after treatment with the glycolysis inhibitor sodium mono-iodoacetate.(ABSTRACT TRUNCATED AT 250 WORDS)