Cytotoxic mechanisms of IL-4 polarized CTLs (101.28)

Abstract

Abstract IL-4 down-regulates perforin and granzymes and depresses rapid (4 hr) cytotoxic T lymphocyte (CTL) killing. Curiously, IL-4 can increase anti-tumor immunity in animal models. We wanted to know how IL-4 polarized CTLs kill and found that they have potent delayed cytotoxicity. We cultured BALB/c mouse splenocytes with conA and 500 units/ml mouse IL-4 or IL-2 for 3 days and then re-cultured the cells for 3 days with cytokines without conA. The IL-4 CTLs were polarized as indicated by expression of the IL-4 inducible lipase PLRP2. By flow cytometry, IL-4 CTLs expressed Grz B at lower levels than IL-2 CTLs. We assayed cytotoxicity using anti-CD3-redirected death of P815 tumor cells. Death was measured at 48 hrs by loss of EGFP+ P815 cells using flow cytometry with cell count beads to account for dead cell disintegration. Cytotoxicity by the IL-4 CTLs was 80% at effector lymphocyte to P815 (E:T) ratios of 1:10. IL-4 CTLs had perforin-independent mechanisms, with similar activity for WT and Prf1-/- CTLs. We monitored T cells for death receptor ligands. Quantitative RT-PCR indicated that IL-4 cells maintained comparable levels of mRNA for LTβ, LIGHT, TRAIL and FasL, but had lower levels of TNFα and TNFβ, than IL-2 CTLs. We conclude that IL-4 polarized CTLs have potent cytotoxicity which could be mediated by death receptor ligands and/or by novel IL-4 inducible potential cytotoxins. Supported in part by NIH grants R01CA38942, T32CA09563, P20 RR-016464 & P20-RR015581.