MHC Class I Deficiency Overview

MHC Class I Deficiency Overview

• MHC Class I deficiency impacts the expression of CD8+ cytotoxic T cells.
• Individuals lacking MHC Class I show a compromised immune response related to these T cells.

Viral Infections and MHC Expression

• Individuals with CD8+ T cell deficiency can still express MHC Class I during viral infections, but production is limited to a few MHC molecules.

T Cell Count Dynamics

• Low CD8+ T cell counts alongside high CD4+ T cell counts can occur during maturation.
• Double-positive T cells interact with CD4+ and MHC Class II tightly; however, single-positive cells interact weakly with CD8+ and MHC Class I, leading to failed interactions.

T Cell Subtypes in Deficiency

• Patients may exhibit low counts of alpha-beta T cells and predominantly gamma-delta T cells.
• Gamma-delta T cells are unique in that they do not require MHC for recognition, indicating a deficiency of essential alpha-beta T cells.

Immunoglobulin Levels

• Elevated serum IgG levels are common in patients with MHC Class I deficiency.
• The absence of MHC Class I leads to increased antibody production as a compensatory mechanism for reduced cellular immunity.

Impact of TAP/Tapasin Defects

• A defect in TAP (Transporter associated with Antigen Processing) and tapasin affects MHC Class I loading.
• Despite the presence of tapasin, a defect hinders MHC Class I loading, resulting in impaired immune responses.