Activation of T lymphocytes for adhesion and cytokine expression by toxin-conjugated anti-CD3 monoclonal antibodies

Background Immunosuppressive drugs that target T cells are useful for prolo nging allograft survival. The anti-CDS immunotoxin FN18-CRM9 has been shown to effectively prolong renal allograft survival in a rhesus monkey model o f transplantation However, immunotoxin-treated monkeys showed increased lev els of inflammatory cytokines and produced antibodies to donor proteins, To better understand the role of FN18-CRM9 in the production of cytokines and anti-donor antibodies in the monkey model, we examined whether this immuno toxin elicits functional responses in T cells. Methods. Purified normal rhesus monkey T cells (>98% purity) were incubated with immunotoxin FN18-CRMS or the unconjugated anti-CD3 monoclonal antibod ies and then examined for changes in protein tyrosine phosphorylation, adhe sion to fibronectin, gene expression, and proliferation in the presence or absence of anti-CD28 monoclonal antibodies (mAb) and interleukin-a. Results. Immunotoxin treatment of T cells in vitro increased protein tyrosi ne phosphorylation, cell adhesion to the extracellular matrix, and expressi on of the inflammatory cytokines interferon-gamma and tumor necrosis factor -cu, These immunotoxin effects were similar in magnitude to those induced b y the unconjugated mAb, In contrast, immunotoxin-induced T cell proliferati on was markedly less than that induced by the unconjugated mAb, Interesting ly, the mitogenic molecules IL-2 and anti-CD28 mAb did not prevent immunoto xin-induced inhibition of cell proliferation. Conclusions. The activation of T cells for protein phosphorylation, adhesio n, and cytokine expression strongly suggests that the actions of FN18-CRMS in vivo are not limited to the inhibition of protein synthesis.