Absence of natural killer cells in a child with pure red blood cell aplasia

A 16‐year old boy was known to suffer from red blood cell (RBC) aplasia from the age of 4 years. Peripheral blood lymphocytes (PBL) from the patient were found to lack natural killer (NK) cytotoxic activity, even after stimulation with α‐interferon. His PBL also lacked Leu‐7⁺ and Leu‐11⁺ cells, although his granulocytes showed normal expression of the Leu‐11 marker. The lack of NK cells did not seem to result from the various immunosuppressive treatments he received, since the NK deficiency was noted 2 years after he stopped receiving such treatment. The possibility is discussed that lack of NK cells may lead to the development of RBS aplasia if NK cells play a role in promoting the production of RBC.