Leukocyte-dependent antibody in sheep immunized with murine mastocytoma cells.

Sheep serum removed after hyperimmunization with murine P-815 mastocytoma cells was fractionated and two types of cytotoxic antibody were isolated. Complement-dependent antibody (CDA) was detected in the IgM and IgG1 fractions whereas "leukocyte" -dependent antibody (LDA) was found in the IgG1 and IgG2 fractions. Effector cells that mediated LDA cytotoxicity were isolated from sheep blood but not from sheep lymph, showing that recirculating lymphocytes do not have LDA effector function. Removal of adherent cells from blood leukocyte suspensions reduced antibody-mediated cytotoxicity, suggesting that LDA effector leukocytes may be a heterogenous population containing both adherent and nonadherent cells.