Anti-CD45 augments response of a Th2 clone to TCR cross-linking

The CD45 molecule is a transmembrane tyrosine phosphatase that may be associated with the T-cell receptor (TCR). This has led to the suggestion that CD45 may be important for the regulation of signal transduction in T cells. This idea is supported by the finding that antibodies against CD45 are comitogenic in proliferation assays. In the present work, we have examined the comitogenicity of CD45 antibodies by studying the effect of CD45, CD45RA, and CD45RB monoclonal antibodies (MoAbs) on proliferation of D10 cells induced with T-cell receptor (TCR) MoAbs. In addition interactions with some other proliferation inducing agents namely CD3 antibodies, lectins, and IL-2, are examined here. We have found that in general the CD45 MoAbs would significantly enhance proliferation induced by a wide spectrum of TCR MoAbs and other proliferation inducing agents, with some minor quantitative differences. The CD45 and CD45RB MoAbs were equally potent in their comitogenic activity while the CD45RA antibody was somewhat less potent. The comitogenic effect was maximal when CD45 antibodies were added simultaneously with the TCR MoAb, but significant comitogenicity could be detected when CD45 MoAbs were added up to 24 h after the initiation of the culture indicating that the CD45 antibodies also affect other processes than the initial signal transduction cascade.