Human Biology · MU Plovdiv

40. MHC – complex. Structure and function. MHC restriction.

Inside: 15 sections · 2 labelled pictures · 10 flashcards · 8 min

Topic 40 of 66 in the MU Plovdiv syllabus for Human Biology (Dental Medicine, Year 1). The free AceMed note covers it in 15 sections, about 1,098 words (8 min of reading), with 10 flashcards.

In this note

  1. Molecules of cell-mediated immunity.
  2. Overview of Cell-Mediated Immunity
  3. The T Cell Receptor (TCR)
  4. Types of T Cell Receptors
  5. Structure and Function of TCR2
  6. Comparison with Antibodies
  7. Gamma Delta (γδ) T Cells
  8. TCR Signal Transduction
  9. How T Cells Recognize Antigens
  10. Major Histocompatibility Complex (MHC)
  11. Genetics of the MHC
  12. Structure of MHC Molecules
  13. MHC Expression and Tissue Distribution
  14. MHC Co-receptors on T Cells
  15. MNEMONICS

Overview of Cell-Mediated Immunity

  • Cell-mediated immunity is the arm of the immune system primarily carried out by T lymphocytes (T cells).
  • These T cells detect and respond to infected or abnormal cells, rather than free-floating pathogens in bodily fluids.
  • T cells rely on a specialized surface protein called the T cell receptor (TCR) to recognize antigens presented to them by other cells.

The T Cell Receptor (TCR)

  • T cells have surface receptors that are structurally distinct from the immunoglobulins found on B cells.
  • The T cell receptor is never secreted; it is anchored in the cell membrane.
  • TCR belongs to the immunoglobulin superfamily of proteins but functions exclusively on the cell surface.
  • The receptor allows T cells to recognize processed fragments of protein antigens presented by other cells.

Types of T Cell Receptors

  • There are two main types of TCRs:
  • TCR2, which is composed of alpha (α) and beta (β) chains, is found on over 90 percent of T cells.
  • TCR1, which is composed of gamma (γ) and delta (δ) chains, is present on a small population of T cells.

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