T Cell-Independent Macrophage Activation in Scid Mice

Abstract

Macrophages play a critical role in immune regulation and resistance of the host to infection. Of particular importance is the activation of macrophages for microbicidal and tumoricidal activity and expression of cell surface molecules such as class II MHC (Ia) antigens (Unanue 1984). The ability of T cells to mediate these responses has been extensively documented and occurs via the production of specific cytokines, most notably IFN Y (Schreiber and Celada 1985; Unanue 1981). However, the scid mouse now provides an important new model for studying the pathways of macrophage activation (Bosma et al 1983). The scid mutation results in abnormal rearrangement of genes encoding antigen specific lymphocyte receptors and is characterized by the absence of functional T and B lymphocytes (Schuler et al 1986). This defect is specific for the lymphoid lineage since erythroid and myeloid functions are normal. We have therefore used the scid mouse to examine macrophage development in the absence of T cells. Our results demonstrate that macrophage activation can occur in a T cell-independent manner and that this may constitute an important mechanism of natural resistance to infection.

This study was supported by grants from the National Institutes of Health, Eli Lilly Research Laboratories, Monsanto Company and Genentech Inc.