Successful haploidentical hematopoietic stem cell transplantation in a patient with SCID due to CD3ε deficiency: need for IgG-substitution 6 years later

BACKGROUND

The CD3 co-receptor complex is essential for signal transduction after specific binding of the T-cell receptor (TCR). CD3E encodes the CD3ε chain, one of the protein components (γ-, δ-, ε- and ζ-chain) of the CD3 co-receptor. As previously reported in one family CD3ε deficiency causes SCID.

PATIENT

We report on a patient with SCID due to CD3ε deficiency treated by HLA-haploidentical stem cell transplantation (SCT) (donor: mother) 15 years ago which resulted in development of normal T- and B-cell immunity. Despite conditioning donor cell engraftment was confined to T cells, while all other blood cell lineages remained of patient origin (split chimerism). In spite of normal functions, T-cell numbers never reached normal levels and naïve CD45+RA+ T-cells remained low. At 6 years after SCT the patient developed signs of humoral immunodeficiency, requiring regular substitution of IgG.

RESULTS

In a retrospective genetic work up 11 years after SCT, a homozygous splice site mutation in CD3E was identified resulting in the loss of CD3ε protein. The loss of B-cell function as observed in the patient was reflected by a lack of switched memory B cells. To rule out a primary role of CD3ε in B-cell function we studied expression of CD3E in B-cells which was found not to be expressed.

DISCUSSION

The clinical presentation of a secondary loss of specific humoral immunity in this constellation of split chimerism after allogeneic haploidentical SCT is unusual and unexpected in a patient with a primary T-cell defect. A most likely explanation is the gradual loss of T-helper-cell function.

Proliferation studies on chromosome preparations of bone marrow in hematological disease

The growth rate of neoplastic cells has been the subject of numerous scientific and diagnostic approaches. The study presented here analyses the relationship between mitotic activity in standardised cytogenetic bone marrow preparations from three haematological diseases and diagnostic and clinical parameters, most importantly the outcome. The disorders studied were: Acute lymphoblastic leukemia (ALL) (N=107), chronic myeloid leukemia (CML) (N=166) and aplastic anemia in childhood (AA) (N=39). A strict protocol of quantitative standardisation of cytogenetic slides was adhered to ensuring comparability both cross-sectionally and longitudinally. The samples were studied after short-term incubation without mitogenic in vitro stimuli. The most important findings include: i) ALL: Immunological subtypes can be differentiated according to their proliferation profile; there is a striking difference between childhood and adult ALL in proliferation activity; most importantly initial proliferation is much higher in patients who will relapse than in those with stable remission. ii) CML: Philadelphia-positive CML shows proliferation activities quite distinct from Philadelphia-negative CML; however there is only a small change in the proliferative activity from the chronic phase to the accelerated phase or blast crisis. iii) AA: Very low proliferation scores rise quickly to near normal levels during immunosuppressive therapy in most patients. Higher levels at diagnosis are associated with a faster and better response to therapy. In conclusion, assessment of the proliferative activity in cytogenetic preparations made from bone marrow samples of patients with haematological disease may add valuable information as to diagnostic sub-groups and clinical course and may contribute to therapeutic decisions.