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MHC Deficiency

Topic updated on 05/18/17 12:41pm

Snapshot
  • An infant child is brought to the pediatrician for the evaluation of recurrent infections. The mother reports that her child has been having frequent respiratory and skin infection. The mother is not aware of any diseases that run in the family that will result in an increased susceptibility to infection. A ↓ MHC class 1 expression on peripheral blood mononuclear cells is noted on flow cytometry. Further genetic testing shows the infant has a mutation in the tapasin protein. (MHC class I deficiency)
MHC Class I Deficiency (Bare Lymphocyte Syndrome Type I)
  • Clinical definition
    • an immunodeficiency syndrome secondary to defects in
      • TAP 1, TAP 2, and tapasin which are involved in
        • transporting the antigen peptide (TAP 1 and 2) into the endoplasmic reticulum and
          • loading (tapasin) the antigen peptide into the MHC
  • Presentation
    • frequent bacterial infections such as
      • upper and lower respiratory infections
      • skin infections
  • Laboratory findings
    • ↓ or decreased MHC class I expression
    • ↓ NK cell killing activity
    • ↓ CD8+ T-cells
  • Differential
    • other immunodeficiency syndromes such as
      • common variable immunodeficiency
  • Diagnosis
    • definitive diagnosis is accomplished with
      • flow cytometry, which shows
        • ↓ MHC I expression on peripheral blood mononuclear cells
  • Treatment
    • management focuses on controlling the infection with
      • antibiotics
MHC Class II Deficiency (Bare Lymphocyte Syndrome Type II)
  • Clinical definition
    • an immunodeficiency syndrome possibly secondary to defects in
      • DNA-binding regulatory molecules of the class II MHC promoter
  • Presentation
    • infections with
      • viruses
      • bacteria
      • fungi
      • protozoa
    • the clinical scenario may be similar to severe combined immunodeficiency (SCID) because
      • MHC class II plays an important role in
        • the maturation and functioning of
          • T- and B-cells
  • Laboratory findings
    • normal number of T- and B-cells in the peripheral blood
    • hypogammaglobulinemia
    • absence of MHC class II on B cells
    • ↓ CD4+ T-cells
  • Differential
    • other immunodeficiency syndromes such as
      • SCID
  • Diagnosis
    • definitive diagnosis is accomplished with
      • flow cytometry, which shows
        • ↓ MHC II expression on peripheral blood mononuclear cells
  • Treatment
    • management focuses on controlling the infection with
      • antibiotics and immunoglobulin therapy


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