Participation of CD11a‐c/CD18, CD2 and ROD‐binding receptors in endogenous and interleukin‐2‐stimulated NK activity of CDS‐negative large granular lymphocytes

The effect of RGD-sequence-containing pentapeptides and monoclonal antibodies (MAbs) against the adhesion molecules CD11a-c/CD18, ICAM-1 (CD54) and CD2 on the binding and cytotoxicity of endogenous (freshly purified) and IL-2-stimulated CD3-negative NK cells has been studied. Antibody to CD18 exerted the most significant inhibition of adhesion and cytotoxicity of endogenous NK cells to MOLT-4 lymphoma cells, followed by antibodies to CD2 and CD54. Antibodies to either CD11a, CD11b or CD11c did not inhibit adhesion when used separately, whereas as a mixture their inhibitory capacity was as strong as that of anti-CD18. Antibodies against CD18, CD54 and CD2 exerted an additive effect on the inhibition of adhesion. Their combination eradicated the binding of endogenous NK cells. The RGD-containing peptide did not inhibit the binding or cytotoxicity of freshly purified NK cells to MOLT-4, whereas some inhibition was detected against the adenocarcinoma cell line COLO-205. According to FACS analysis, IL-2 increases the expression of CD2 and CD54 on NK cells. However, the relative contribution of the adhesion molecules to the NK cell binding did not change as a result of the stimulation with IL-2. The RGD-peptide substantially inhibited the binding of IL-2-stimulated killer cells to COLO, and the combination of this peptide with MAbs to CD18, CD54 and CD2 practically blocked the adhesion. Our results indicate that both CD11a-c/CD18- (involving the 3 heterodimers) and CD2-dependent adhesion pathways are used by LGL in endogenous and IL-2 stimulated natural killing. In addition, RGD-binding receptors are involved in adhesion to some target cells.