Genetic loci responsible for the encoding of minor lymphocyte stimulatory antigens. There are at least two unlinked loci (in the mouse) and they appear to be separate from the MAJOR HISTOCOMPATIBILITY COMPLEX and MINOR HISTOCOMPATIBILITY LOCI. The mouse mammary tumor virus (see MAMMARY TUMOR VIRUS, MOUSE) has the ability to integrate into these loci. The antigens induce strong T-cell proliferative responses in mixed lymphocyte reactions.

Endogenous superantigens responsible for inducing strong proliferative responses in T-cells in mixed lymphocyte reactions (see LYMPHOCYTE CULTURE TEST, MIXED). They are encoded by mouse mammary tumor viruses that have integrated into the germ line as DNA proviruses (MINOR LYMPHOCYTE STIMULATORY LOCI).

White blood cells formed in the body's lymphoid tissue. The nucleus is round or ovoid with coarse, irregularly clumped chromatin while the cytoplasm is typically pale blue with azurophilic (if any) granules. Most lymphocytes can be classified as either T or B (with subpopulations of each), or NATURAL KILLER CELLS.

Substances that are recognized by the immune system and induce an immune reaction.

Morphologic alteration of small B LYMPHOCYTES or T LYMPHOCYTES in culture into large blast-like cells able to synthesize DNA and RNA and to divide mitotically. It is induced by INTERLEUKINS; MITOGENS such as PHYTOHEMAGGLUTININS, and by specific ANTIGENS. It may also occur in vivo as in GRAFT REJECTION.