IMMUNOLOGY AND HOMOLOGOUS RECOMBINATION - STUDY OF T-CELLS ONTOGENY

One of the most powerful methods for studying any living organism is to identify a << monster >> that can be compared with its << normal >> counterpart. Recently, it has become possible to create mice carrying almost any chosen mutation using homologous recombination. This technique has been particularly useful for studying the immune system. Here we discuss four different mutant mice, focusing on their relevance to T-cell development : (1) mice unable to express beta-2 microglobulin, a protein required for cell surface expression of major histocompatibility complex (MHC) class I molecules; (2) mice in which expression of CD8, a coreceptor on class I restricted T cells, has been abrogated; (3) mice in which expression of CD4, a coreceptor on class II restricted T cells, has been abrogated; (4) mice lacking cell surface expression of MHC class II heterodimers due to a drastic mutation in the A-beta gene.