Evidence for the existence of distinct heterogeneity among the peripheral CD4 −CD8 − T cells from MRL- lpr/lpr mice based on the expression of the J11d marker, activation requirements, and functional properties

Abstract

Autoimmune-susceptible, MRL- lpr/lpr ( lpr) mice develop a profound lymphadenopathy resulting from the accumulation of CD4 −CD8 − (double-negative, DN) cells in peripheral lymphoid organs. The source and the mechanism of this abnormal accumulation of cells is still unknown. Recently, we reported that a significant number (~35%) of the CD4 −CD8 − cells expressed J11d, a marker expressed by immature thymocytes but not by mature functional peripheral T cells. In the present study, we investigated the phenotype, growth requirements, and functional properties of purified J11d + and J11d − subpopulations. Using the mAb, F23.1, which recognizes a TCR determinant encoded by the Vβ8 gene family, it was observed that ~30% of the J11d + and J11d − DN cells expressed this determinant. Further studies on the thymus revealed that J11d + DN cells from lpr thymus also contained F23.1 + cells (~25%), whereas, similar cells from normal MRL-+/+ mice were all F23.1 −, consistent with earlier reports in other normal strains. Further phenotypic studies revealed that the peripheral J11d + and J11d − cells from lpr mice were similar in expressing CD3, Ly-5 (B220), and Ly-24 (Pgp-1) determinants. When stimulated with phorbol myristic acetate (PMA) and recombinant IL-2 (rIL-2), only J11d − cells but not J11d + cells responded by proliferation. However, in the presence of calcium ionophore (A23187) and PMA, both J11d + and J11d − subpopulations proliferated by producing and responding to endogenous IL-2 but not IL-4. The lymph node T cells from 1-month-old MRL- lpr/lpr mice responded strongly when stimulated with PMA + rIL-4 or PMA + rIL-6. In contrast both J11d + and J11 − subpopulations failed to respond when similarly stimulated. The J11d + but not J11d − cells demonstrated spontaneous cytotoxic activity against the NK-sensitive YAC-1 tumor targets. The J11d − cells did not exhibit cytotoxic potential in spite of culture with PMA + rIL-2. Even after repeated culture in vitro with PMA + A23187 or PMA + rIL-2, both J11d + and J11d − subpopulations failed to express the mature phenotype bearing CD4 and/or CD8 antigens. The present study demonstrates the expansion of unique J11d +, αβ-TCR +, DN T cells with cytotoxic potential in lpr mice and further suggests the existence of phenotypic and functional heterogeneity among the abnormal lpr DN cells.