MONOCLONAL ANTI-IGM CAN SEPARATE T-CELL FROM B-CELL PROLIFERATIVE RESPONSES IN THE FROG, XENOPUS-LAEVIS

Abstract

The role of surface IgM-positive (slgM+) lymphocytes in frog mitogen responses and mixed lymphocyte reactions was examined. A murine monoclonal antibody with specificity for X. laevis IgM was produced. The anti-IgM activity was not inhibited by glycoproteins other than Xenopus IgM but could be inhibited with periodate-treated frog IgM. Fluorescent microsphere-coupled anti-IgM was used to show that adult and larval thymocytes had few sIgM+ lymphocytes whereas spleens contained 19-34% sIgM+ lymphocytes. The spleens of larvally thymectomized adults were greatly enriched for sIgM+ cells. Lymphocyte suspensions were depleted of sIgM+ cells by incubation of spleen cells on plastic petri dishes coated with anti-IgM monoclonal antibody. Compared with unseparated controls, the nonadherent cells cultured in serum-free medium were enriched for concanavalin A and phytohemagglutinin (PHA) mitogen responses and mixed lymphocyte culture (MLC) reactivity. Nonadherent cells were partially depleted of (LPS) mitogen responsiveness. Depletion or enrichement of the mitogen response was not a result of changes in kinetics or dose-response characteristics of the cells. In 1% fetal calf serum-supplemented cultures, the LPS response was not depleted whereas the PHA response was still enriched. Thus, thymus-dependent and thymus-indpendent mitogen and MLC responses can be separated by the criterion of sIgM positivity in this anuran species.