Reconstitution of Clq after bone marrow transplantation in patients with severe combined immunodeficiency

The serum concentration of Clq, a subunit of the first component of complement, was followed in six patients with severe combined immunodeficiency disease (CID) prior to, during, and after bone marrow transplantation. The serum level of Clq was found to be diminished in all patients prior to transplant (27-44% of normal). Agematched controls had a serum concentration of 20.2±4.9 μg N/ml, whereas our patients with CID had an average level of 6.3 μg N/ml. One patient failed to have a graft "take" with no evidence of immunological reconstitution, and the Clq remained very low. Of the other five patients with partial or full immunological reconstitution, four of these five had increased serum Clq levels to normal after transplantation. Clear evidence for engraftment was present in three of these four patients. Our data demonstrate the increase of serum Clq after bone marrow transplantation, and the possible usefulness of the serum level of Clq as a marker for evaluating engraftment. Although the etiology of the deficiency of Clq in this group of patients is unknown, an understanding of the mechanism(s) for "reconstitution" of Clq after marrow transplant has important clinical implications.