We examined the effect of dibutyryl cAMP (dbcAMP) on the expression of LFA‐1 (CD1 la/CD18), Mac‐1 (CD11b/CD18), and VLA‐4 (CD49/CD29) and on eosinophilic differentiation of a human leukemia cell line, EoL‐1. Dibutyryl cAMP induced eosinophilic differentiation of EoL‐1 cells from 6–9 days after the start of culture with down‐regulation of CD 11a, CD 18, and CD49 expression and up‐regulation of CD11b expression. Changes in integrin expression, except for CD18, were seen predominantly in the fraction containing eosinophilic granule‐positive cells, suggesting that the changes were dependent on eosinophilic differentiation. On the other hand, dbcAMP‐induced changes of integrin expression were reversible and were not seen on day 9 when dbcAMP was removed on day 3, whereas eosinophilic differentiation was still present. A combination of G‐CSF and TNFα, which also induced eosinophilic differentiation of EoL‐1 cells, increased CD11b expression slightly but had no significant effect on the expression of the other integrins. Butyrate and PMA up‐regulated CD11b expression without eosinophilic differentiation. The results collectively suggest that the regulation of integrin expression on EoL‐1 cells is partly dependent and partly not dependent on eosinophilic differentiation. The possible involvement of protein kinase A and protein kinase C in these changes is suggested.
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