Expression of the Alpha-Chain Gene in Heterogeneous IgA Immunodeficiency

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Abstract
Five heterogeneous IgA‐immunodeficient patients were analysed for expression of the α‐chain gene. The number of surface IgA‐bearing B cells was low in four patients Southern blot analysis indicated no deletion of immunoglobulin structural genes coding for Cα or α switching‐region genes. The number of surface IgM and IgA double‐bearing B cells increased in some patients. Addition of recombinant tnterieukin 4 (rIL‐4). rIL.‐5. and rIL‐6 to the normal B cells enhanced IgA production. However. B cells of the patients showed no or one‐third lower IgA production in response to these lymphokines, even though there was proliferation ill 4, rIL ‐5, and rIL‐6 induced low or no expression of α mRNA of the patients B cells These results suggested that the patients lacked B cells able to produce transcripts for the IgA heavy chain, and that some patients’B cells might be defective at the switch‐recombination process from u to a or from μ to α or from μ and α to α.