The mixed leukocyte culture (MLC) test is an in vitro model of the recognition phase of the homograft response. For the most part, activation in MLC is dependent on differences of the major histocompatibility complex (MHC). Our present studies in the mouse suggest that activation is primarily associated with differences of genetic regions of the MHC other than those which control the serologically defined (H-2) antigens. These differences do not lead to cytotoxic or agglutinating antibody formation despite extensive immunization; we have called these differences lymphocyte-defined (LD) differences. The strongest stimulation in MLC is associated with differences of the Ir region. It is possible that the Ir product is the T cell receptor and that it is this same molecule which can act as the stimulatory agent in MLC. Other possibilities are discussed.

Animals↗

PubMed1972

Responsiveness of germfree mice in mixed leukocyte culture. Reexamining the nature of the responding unit.

Conventional (cv) and germfree (gf) mice are able to give a good proliferative response to allogeneic cells in the mixed leukocyte culture (MLC) test, while the response to xenogeneic stimulating cells has been in question. Previous studies by others have suggested only a low MLC response in cv animals and none in gf ones. We have found that both cv and gf animals can give a good MLC response to xenogeneic as well as allogeneic cells. These findings are of importance for our understanding of both MLC stimulation and response.

Animals↗

PubMed1972

Genetic and immunological complexity of major histocompatibility regions.

There are genetic differences within the major histocompatibility complex of the mouse which lead to skin graft rejection but which cannot be detected serologically. When confronted with these differences on allogeneic cells, lymphocytes proliferate in vitro. In other cases, in vitro lymphocyte proliferation but no skin graft rejection is associated with loci that are linked to but genetically separable from the loci controlling the serologically defined antigens.

Alleles↗

PubMed1972

Allogeneic and xenogeneic response in mixed leukocyte cultures.

The mixed lymphocyte culture (MLC) test has been regarded as an in vitro model of the recognition or sensitization phase of the homograft or graft-versus-host reaction. It has been suggested that the graft-versus-host response in vivo is less in xenogeneic combinations than in allogeneic ones and that there is a similar quantitative relationship in MLC responses. Given the above interpretation of the MLC test, this could suggest that the lesser reactivity in xenogeneic combinations may be due to a lesser recognition of the stimulus. We have done nine experiments testing allogeneic and xenogeneic combinations in MLC, largely in combinatorial fashion. The results indicate that the response in xenogeneic MLC may be as great as that in allogeneic MLC and that, as in different allogeneic mixtures, there is great variation in the extent to which xenogeneic mixtures may respond.

Animals↗

PubMed1972