Inherited immune disorders
MHC class II deficiency
MHC class II deficiency impairs the display of signals that help immune cells recognize threats and coordinate a response. It causes severe combined immune dysfunction, often with infections, chronic diarrhea and poor growth.
Other names and abbreviations
BLS II · BLS2 · MHC II deficiency · HLA class II deficiency · Bare lymphocyte syndrome type II · HLA class II-negative severe combined immunodeficiency · MHC class II expression deficiency
Where transplant fits
Allogeneic transplantation is an established treatment and can use an appropriate related or unrelated donor. Donor-derived immune cells may improve protection, but some immune abnormalities can persist because other tissues retain the genetic defect.
Treatment depends on the exact diagnosis, disease stage, prior treatment and the person’s health. These categories are not estimates of donor demand.
Treatment at a glance
- Who it affects
- Usually recognized in infancy or childhood, in both sexes. Several genes controlling MHC class II expression can cause it.
- Other treatment options
- Antimicrobial prevention and treatment, immunoglobulin replacement and nutritional support are used while definitive treatment is considered.
- Cells used for transplantation
- When transplantation is appropriate, the graft contains blood-forming stem cells from a suitable donor. Bone marrow, peripheral blood or cord blood may be selected according to the condition and transplant protocol.
Why the details matter
This is bare lymphocyte syndrome type II, not MHC class I deficiency. Screening based only on T-cell receptor excision circles can miss some affected infants.
Questions to bring to your care team
What is the exact diagnosis or subtype? What is the goal of each treatment option? If transplant is being considered, why does it fit this situation, which cells would be used and what are the alternatives?
Sources and further reading
- Bare lymphocyte syndrome type II
MedlinePlus Genetics, US National Library of Medicine · Accessed 2026-09-05 - Guidelines for hematopoietic stem cell transplantation for inborn errors of immunity
EBMT / ESID Inborn Errors Working Party · 2021
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