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A girl with severe combined immunodeficiency and pronounced malnutrition from chronic diarrhoea is presented. Immunological reconstitution was attempted by transplantation of bone marrow cells from the HL‐A hemiallogeneic father. An initial transplant failed to induce a permanent take of the graft, whereas a second transplant with an increased cell dose ensured a take, which was followed by reconstitution of cell‐mediated immune functions. Fractionation of the transplanted bone marrow cells apparently led to a delay in development of graft‐versus‐host symptoms. Germ‐free isolation and extensive bacterial decontamination markedly reduced the microbial flora and was highly protective against contaminating microorganisms but failed to eradicate completely one strain of Escherichia coli that had invaded the child before institution of this regimen. During a moderate, delayed graft‐versus‐host reaction this strain caused widespread severe infection, to which the child succumbed 10 weeks after the second transplantation. This child presented some additional features, the most conspicuous being a deficiency of erythrocyte adenosine deaminase.

A hemoregulatory peptide (HPSb) associated with mature human granulocytes has been investigated for inhibitory effects on murine hemopoietic stem cells in vitro. Both highly purified peptide from natural sources and a synthetic analog peptide have been investigated in parallel. Strong inhibitory effects were found on myelopoietic colony formation in the dose range 10-13-10-s mol/l. On exceeding this dose, the inhibitory effect disappeared. Moderate to slight inhibitory effects on erythroid colony formation (BFU-E and CFU-E) from adult animals were only seen in 1000 x the optimal doses for myelopoiesis. No effect was found on CFU-E from fetal liver. The peptide thus has a selective effect on myelopoiesis in a certain dose range. A regulatory mechanism for the peptide on hemopoiesis is proposed.