Increased generation of autologous tumor-reactive lymphocytes by anti-CD3 monoclonal antibody and prothymosin α

Abstract

Anti-CD3 monoclonal antibody (mAb) activates in vitro peripheral blood mononuclear cells (PBMC) to lyse a variety of tumor cell lines in a non-major histocompatibility-complex(MHC)-restricted manner [subsequently referred to as anti-CD3-activated killer (AAK) cytotoxicity]. Prothymosin α (ProTα) is a biological response modifier that exerts its effects primarily on mononuclear cells, especially when these cells' effector functions are impaired. In this study, we report that ProTα enhances the AAK cytotoxicity in PBMC from healthy donors. This effect was more profound with cancer patients' PBMC, which were deficient in their ability to respond with enhanced AAK cytotoxicity upon in vitro stimulation with anti-CD3. Thus, cancer patients' PBMC, activated with a combination of anti-CD3 and ProTα, exhibited increased AAK activity and efficiently lysed both autologous tumor and Daudi targets. The ProTα effect on PBMC was demonstrated to involve stimulation of adhesion molecules (CD2, CD18, CD54, CD49f) and CD25 expression, up-regulation of perforin mRNA transcription, increased numbers of perforin-positive (+) cells and elevated production of interleukin-2 (IL-2), interleukin-1β (IL-1β) and tumor necrosis factor α (TNFα). Moreover, effector CD8⁺ and CD56⁺ cells pretreated with anti-CD3 and ProTα contained high cytoplasmic perforin levels and increased expression of IL-1β- and TNFα-specific receptors. The induction of autologous-tumor-reactive CD8⁺ and CD56⁺ lymphocytes in anti-CD3-activated PBMC by ProTα provides an alternative protocol aimed at the improvement of clinical results in cellular adoptive immunotherapy of cancer.