What are HLA molecules?

What are HLA molecules?

The human leukocyte antigen (HLA) system (the major histocompatibility complex [MHC] in humans) is an important part of the immune system and is controlled by genes located on chromosome 6. It encodes cell surface molecules specialized to present antigenic peptides to the T-cell receptor (TCR) on T cells.

What is the function of class II MHC molecules?

The main function of major histocompatibility complex (MHC) class II molecules is to present processed antigens, which are derived primarily from exogenous sources, to CD4(+) T-lymphocytes. MHC class II molecules thereby are critical for the initiation of the antigen-specific immune response.

What cells express MHC class II?

Dendritic cells (DCs), B cells and macrophages constitutively express MHC class II molecules and are regarded as the ‘professional’ antigen-presenting cells (APCs) of the immune system (Fig. 1).

What are HLA classes?

The HLA system is composed of three regions. The class I region corresponds to the genes coding for molecules HLA-A, -B, and -C. In addition, the class II region encodes HLA-DR, -DQ, and –DP. Finally, the class III region, in which genes are encoding for proteins of the complement system and TNF family genes.

What is HLA class I typing?

HLA class I antigens (A, B, and C in humans) render each cell recognisable as “self,” whereas HLA class II antigens (DR, DP, and DQ in humans) stimulate the immune system. 1. Both have been implicated in the rejection of transplanted organs.

What is MHC class II deficiency?

Major histocompatibility complex (MHC) class II deficiency is a rare and fatal primary combined immunodeficiency. It affects both marrow-derived cells and thymic epithelium, leading to impaired antigen presentation by antigen presenting cells and delayed and incomplete maturation of CD4+ lymphocyte populations.

Do macrophages express MHC class I and II?

While MHC class I is ubiquitously expressed by almost all cells, MHC class II is mostly expressed by antigen-presenting cells (APCs) such as monocytes, macrophages, and dendritic cells.

Do T helper cells express MHC Class 2?

T cells require antigens to be processed into short fragments which form linear epitopes on MHC Class II (in the case of helper T cells because they express CD4) or MHC class I (in the case of cytotoxic T cells which express CD8).