Mixed leukocyte culture (MLC) is a biological assay for detecting which of the following?

Mixed leukocyte culture (MLC) is a significant biological assay primarily used to assess the compatibility of HLA (human leukocyte antigen) types, particularly the class II MHC molecules known as HLA-D antigens. MLC involves mixing lymphocytes from two different individuals to observe their proliferative response, which indicates an immune reaction. This response is driven by the recognition of foreign HLA class II molecules present on the lymphocytes of the other participant, leading to cellular activation and division.

This approach is crucial in various clinical settings, particularly in organ transplantation and bone marrow transplantation, where compatibility of HLA types is essential to reduce the risk of graft-versus-host disease (GVHD) and ensure a successful transplant outcome. The assay demonstrates the alloreactive response, which is primarily mediated by T cells recognizing these HLA-D antigens.

In contrast, the other options address different aspects of the immune system. HLA-A and HLA-B antigens are part of the class I MHC molecules, which are primarily involved in presenting endogenous antigens and are not typically assessed via MLC, as this assay focuses on the cellular responses stimulated by foreign class II antigens. Immunoglobulins refer to antibodies produced by B cells,