Abstract
Presenting processed antigens to CD4+ lymphocytes during the immune response involves major histocompatibility complex class II molecules. MHC class II genes transcription is regulated by four transcription factors: CIITA, RFXANK, RFX5 and RFXAP. Defects in these factors result in major histocompatibility complex class II expression deficiency, a primary combined immunodeficiency frequent in North Africa. Autosomal recessive mutations in the RFXANK gene have been reported as being the principal defect found in North African patients with this disorder. In this paper, we describe clinical, immunological and genetic features of 11 unrelated Algerian patients whose monocytes display a total absence of MHC class II molecules. They shared mainly the same clinical picture which included protracted diarrhoea and respiratory tract recurrent infections. Genetic analysis revealed that 9 of the 11 patients had the same RFXANK founder mutation, a 26 bp deletion (named I5E6-25_I5E6+1, also known as 752delG26). Immunological and genetic findings in our series may facilitate genetic counselling implementation for Algerian consanguineous families. Further studies need to be conducted to determine 752delG26 heterozygous mutation frequency in Algerian population.
Highlights
Major histocompatibility complex (MHC) class II deficiency or Bare lymphocyte syndrome (BLS) type II is a primary immunodeficiency, characterized by partial or total absence of constitutive and induced MHC class II molecules (DR, DQ and DP) surface expression on cells normally expressing them [1,2,3].Expression of DR, DQ and DP genes is controlled by four transcription factors encoded by four different genes, CIITA (MIM 600005), RFXANK (MIM 603200), RFX5 (MIM 601863) and RFXAP (MIM 601861) [4,5,6,7]
Major histocompatibility complex type II is a rare immunodeficiency with autosomal recessive transmission
It is due to mutations in four MHC II regulatory genes, defining four complementation groups: MHC2A for group A, RFXANK for group B, RFX5 for group C and RFXAP for group D [8,9,11]
Summary
Expression of DR, DQ and DP genes is controlled by four transcription factors encoded by four different genes, CIITA (MIM 600005), RFXANK (MIM 603200), RFX5 (MIM 601863) and RFXAP (MIM 601861) [4,5,6,7]. The absence of CMH class II molecules surface expression on antigen-presenting cells is behind impaired immune responses in patients with BLS, who present a combined immunodeficiency of early-onset. These individuals are prone to severe and recurrent respiratory and digestive tract infections; whether they are bacterial, viral or fungal. The average life expectancy of these patients is 4 years [15]
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