MHC class II deficiency D81.6

Author: Prof. Dr. med. Peter Altmeyer

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Last updated on: 20.03.2022

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Bare Lymphocyte Syndromes Type II; BLS Type II; MHC- Class II defect

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MHC class II deficiency (major histocompatibility complex/MHC/II deficiency) is a rare (<200 patients worldwide) autosomal recessive primary immunodeficiency caused by LOF mutations in genes of various transcription factors. These mutations lead to a deficiency of MHC class II molecules and ultimately to a disruption of gene regulation. The affected genes encode 4 different regulatory proteins, transcription factors that control the transcription of MHC class II genes. The following genes are affected:

  • RFX51

Their gene products control the transcription of MHC II molecules.

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While the MHC class I complex primarily presents cytosolic peptides, the MHC class II complex primarily presents the cleavage products of exogenous proteins.
Antigen presentation via the MHC II complex occurs mainly on B cells and monocytes. Under the influence of interferon-gamma, this expression is enhanced, or also de-novo expressed on primarily class II negative cells such as fibroblasts or activated T cells.

Mutations in the RFXANK gene are responsible for >70% of all known patients worldwide (Hanna S et al. 2014).

Clinical features
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Recurrent sinubronchial abscess and mycotic infections. Recurrent herpes simplex virus infections. Proceeds in principle like other combined immunodeficiencies without phenotypic specifics.

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The diagnosis can be made by means of flow cytometry. It can be determined that MHC II is absent on cells on which it is normally expressed (such as B cells and monocytes). Total leucocyte counts are normal. CD4 cells are mostly decreased. Serum immunoglobulins are also decreased. Note: Specific antibodies cannot be produced after vaccination.

General therapy
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The clinical picture of the MHC II defect, corresponds to that of a relatively mild combined immunodeficiency (SCID) with recurrent bacterial and kyotic respiratory and skin infections. Finally, a stem cell transplantation in enstrp. centers is inevitable.

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  1. Cai YQ et al (2020) A Novel RFXANK Mutation in a Chinese Child With MHC II Deficiency: Case Report and Literature Review. Open Forum Infect Dis 7:ofaa314.
  2. Cerundolo V et al (2006) Description of HLA class I- and CD8-deficient patients: Insights into the function of cytotoxic T lymphocytes and NK cells in host defense. Semin Immunol 18: 330-336
  3. de la Calle-Martin O et al (2001) Familial CD8 deficiency due to a mutation in the CD8 alpha gene. J Clin Invest 108: 117-123
  4. Hanna S et al (2014) MHC class I and II deficiencies. J Allergy Clin Immunol 134:269-275.
  5. Hauber I et al (1996) More on MHC class II deficiency. N Engl J Med 335: 977-978.
  6. Kallen ME et al (2015) Type II bare lymphocyte syndrome: role of peripheral blood flow cytometry and utility of stem cell transplant in treatment.J Pediatr Hematol Oncol 37:e245-249.
  7. Soe KC et al (2013) Transcriptional coactivator CIITA, a functional homolog of TAF1, has kinase activity. Biochim Biophys Acta 1829:1184-1190.


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Last updated on: 20.03.2022