Definition

Noun: A group of genes located close together on a chromosome, particularly chromosome 6 in humans, that code for proteins (most notably, the Major Histocompatibility Complex or MHC proteins) found on cell surfaces. These proteins are crucial for the immune system to recognize and distinguish between the body's own cells and foreign substances, thereby playing a fundamental role in immune responses, tissue compatibility, and organ transplant rejection.

Usage Examples

• The histocompatibility complex determines an individual's tissue type, which is critical for matching organ donors and recipients.
• Researchers are studying the genes within the histocompatibility complex to better understand autoimmune diseases.
• Variations in the histocompatibility complex can influence an individual's susceptibility to certain infections.

Advanced Usage

• Major Histocompatibility Complex (MHC): This is the primary and most studied component of the histocompatibility complex. It is divided into two main classes:
  • MHC Class I: Presents peptide fragments from inside the cell (e.g., from viruses) to cytotoxic T-cells.
  • MHC Class II: Presents peptide fragments from outside the cell (e.g., from bacteria) to helper T-cells.
• The term is often used in the context of "MHC restriction", which refers to the requirement that T-cells recognize both the antigen and the specific MHC molecule presenting it.

Variants and Related Words

• MHC (Major Histocompatibility Complex): The specific set of genes and molecules most directly responsible for antigen presentation and immune recognition. Often used synonymously with "histocompatibility complex" in immunology.
• HLA (Human Leukocyte Antigen): The name for the Major Histocompatibility Complex in humans. These are the specific proteins coded by the genes on chromosome 6.
• Histocompatibility: (Noun) The property of having compatible tissues, allowing for grafting or transplantation without immune rejection. The histocompatibility complex is the genetic basis for this property.

Synonyms

• MHC gene complex
• Major Histocompatibility Complex (in many contexts, this is the direct synonym)

Related Phrases and Concepts

• Tissue typing: The process of determining the specific HLA/MHC markers of an individual, directly dependent on analyzing the histocompatibility complex.
• Immune recognition: A core function enabled by the proteins of the histocompatibility complex.
• Graft-versus-host disease: A condition where donated immune cells attack the recipient's tissues, heavily influenced by mismatches in the histocompatibility complex.

Noun

1. a family of fifty or more genes on the sixth human chromosome that code for proteins on the surfaces of cells and that play a role in the immune response