CYTOLYTIC LYMPHOCYTES-T - AN OVERVIEW OF THEIR CHARACTERISTICS

Cloned T cells have been useful for assessing the lytic potential of distinct T cell subsets and for determining the relative contribution of different effector mechanism involved in the lytic process. Alloreactive CD8+ murine T cell clones and cloned murine CD4+ T(H)1 and T(H)2 T cells reactive with nominal antigen (ovalbumin) lysed nucleated target cells bearing antigen or coated with anti-CD3 monoclonal antibody in a short term Cr-51-release assay. These clones were also evaluated for their ability to lyse efficiently sheep erythrocyte (SRBC) target cells coated with anti-CD3 mAb by a mechanism (presumably involving membrane damage) that does not involve nuclear degradation. Three patterns of lysis were observed: CD8+ and some CD4+ T(H)2 effector cells lysed efficiently nucleated target cells and anucleated SRBC coated with anti-CD3 mAb. However, CD4+ T(H)1 (and a few T(H)2) T cells which lysed nucleated target cells bearing antigen or coated with anti-CD3 mAb did not lyse efficiently the SRBC coated with anti-CD3 mAb. One CD4 bearing T(H)2 cell failed to lyse efficiently either nucleated target cells or anucleated SRBC coated with anti-CD3 mAb. These results indicate that both T(H)1 and T(H)2 clones have lytic capabilities. Furthermore, they suggest that some but not all T(H)2 murine T cell clones have lytic characteristics similar to those of conventional CD8+ CTL. However, it is not certain how these patterns of lysis of target cells in vitro relates to the capacity of CTL to lyse such target cells in vivo.