Human thymus lymphoid tissue (HTL) antigen, complement receptor and rosette formation with sheep erythrocytes of the lymphocytes from primary immunodeficiency diseases.

The presence of human thymus lymphoid tissue (HTL) antigen, which we have proposed as a marker of thymus-derived lymphocytes (T cells) in human beings, complement receptor and rosette formation with sheep erythrocytes were tested on the lymphocytes from various immunodeficiency diseases. It is postulated that both T and B cells are reduced in severe combined immunodeficiency, B but not T cells are defective in infantile X-linked agammaglobulinaemia, and both T and part of B cell populations (IgA producers) are impaired in ataxia telangiectasia. The HTL antigen-positive cells (HTLC) were reduced in two cases of ataxia telangiectasia and a case of severe combined immunodeficiency. HTLC were present in numbers comparable to normal controls in two cases of X-linked agammaglobulinaemia and two cases of isolated IgA deficiency. The number of rosette-forming cells with sheep erythrocytes (RFC) in ataxia telangiectasia were rather higher than controls, which means that rosette formation is not specific to T cells, at least in some situations, although there is some evidence suggesting that it is a property of T cells in normal conditions. The complement receptor lymphocytes (CRL) have been suggested to be B cells in the mouse. However, CRL were present in normal numbers in the cases of X-linked agammaglobulinaemia. This indicates that CRL are not necessarily antibody-forming cells in man.