Individuals who have abnormally low levels of immune molecules known as antibodies have an increased susceptibility to infection with certain types of bacteria. By analyzing one such person, Jacques J.M. van Dongen and colleagues, at Erasmus MC, University Medical Center Rotterdam, Netherlands, have identified a new genetic cause of antibody deficiency, mutations in the CD81 gene.
Mutations in the CD19 gene, which generates a protein that functions in a complex with CD21, CD81, and CD225, are known to be a cause of antibody deficiency. The patient studied by van Dongen and colleagues had impaired antibody responses and an absence of CD19 expression on B cells (the immune cells that produce antibodies). Surprisingly, no mutations were detected in the patient's CD19 genes.
However, mutations were detected in both copies of the CD81 gene, and this was associated with a complete lack of CD81 expression on immune cells in the blood.
Further analysis using B cells from the patient revealed that CD81 is required for CD19 membrane expression, providing mechanistic insight into the antibody deficiency caused by CD81 mutation.
The research appears in the Journal of Clinical Investigation.
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