The biochemical basis of immunodeficiency disease

Severe combined immunodeficiency: treatment by bone marrow transplantation in 15 infants using HLA-haploidentical donors

In 15 infants with severe combined immunodeficiency (SCID), immunological reconstitution was attempted by bone marrow transplantation (BMT) from HLA-haplo-identical parents. To prevent graft versus host disease (GvHD), marrow grafts were depleted of contaminating T-lymphocytes using lectin agglutination and rosette formation with sheep red blood cells. Thirteen patients received transplants without undergoing prior cytoreductive conditioning. Eleven of these developed donor-dependent T-cell functions, two failed to do this. One of these two as well as two further patients received cytoreductive treatment prior to repeat and to first transplants and in two, complete lymphohemopoietic reconstitution was observed. Of the 15 patients who received transplants, 11 are currently alive. Two recently treated patients remain in the hospital, nine are at home with stable T-cell functions. Normal humoral immune functions have developed upto now in three patients. In the others, gamma globulins are regularly substituted. Complications of acute or chronic GvHD were not observed with the exception of one case who developed transient GvHD of the skin. These results suggest that in a majority of patients with SCID, T-cell functions can develop without GvHD following haploidentical, T-cell-depleted BMT. Exceptional patients require preconditioning to allow donor cell engraftment, an approach that also appears to facilitate reconstitution of humoral immune functions.

Purine enzymes and immune function

The term immune function is taken to mean the process by which lymphocytes respond to an antigenic challenge. This response involves cell division and differentiation, which depend on purine nucleotides. The present state of knowledge relating events at the cell surface to the necessarily increased rate of purine de novo synthesis, and the modulation of purine nucleotide interconversions through the mediation of putative intracellular messengers, is reviewed. These physiological processes are related, where possible, to some genetic and pharmacologically induced perturbations of the systems involved.

Purine metabolism in relation to leukemia and lymphoid cell differentiation

A number of inborn errors of purine metabolism have been associated with immunodeficiency diseases. From studies to the possible mechanism(s) leading to the defects in the immune system, it appeared that the accumulation of deoxyATP and deoxyGTP and the subsequent inhibition of ribonucleotide reductase played an important role. The inhibition of methylation pathways through the accumulation of s-adenosylmethionine seems to be a second valid concept. The amount to which certain subtypes of lymphoid cells were affected by the enzyme deficiencies was strongly related to the enzymatic make-up of the cells. Lymphoid cells from different maturation stages could be affected in a specific way, depending on the different enzyme activities of these cells. Studies on human lymphoblastic leukemias showed that, related to the immunological subtype, the different leukemias could be characterized by a different enzymatic make-up. In this paper we discuss the possibilities for a specific enzyme directed chemotherapy, directed against specific subtypes of human lymphoblastic leukemias. Experimental evidence indicates that for example the adenosine deaminase inhibitor 2'deoxycoformycin can be used as a specific drug against acute lymphoblastic leukemia with the T cell phenotype.

Deoxyadenosine triphosphate accumulation in erythrocytes of deoxycoformycin-treated mice

The accumulation of deoxyadenosine triphosphate (dATP) in erythrocytes of mice treated with the adenosine deaminase inhibitor deoxycoformycin was studied in an attempt to establish and evaluate a model system for the study of at least some biochemical aspects of hereditary adenosine deaminase deficiency. Mouse erythrocytes in vitro readily phosphorylated deoxyadenosine to dATP, and this nucleotide was relatively stable once formed. dATP accumulated in vivo in mice treated with deoxycoformycin both as a function of dose from 0.25 to 10 mg/kg, and with time after administration. Major sources of the deoxyadenosine used for dATP formation in vivo appear to be normoblast nuclei produced during erythropoiesis, and dying cells; minor sources would appear to include dietary DNA, overproduction of deoxyribonucleotides, and DNA repair.