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CD27 and CD134 ligand (CD134L) are two B cell co-receptors for T_h cell activation-induced ligands (i.e. CD70 and CD134) that promote differentiation of B cells into plasma cells and high-rate antibody production respectively. We explored the CD27 pathway and T cell CD134 expression in common variable immunodeficiency (CVID), a disease characterized by a lack of plasma cells and low Ig serum levels. Twelve patients were compared to seven healthy controls. We found a low percentage of circulating CD27⁺ B cells in seven patients and B cell CD27 expression was not up-regulated by in vitro activation in two of them. Importantly, the number of circulating CD27⁺ B cells was correlated with the severity of the disease--the patients with the lowest CD27⁺ B cell counts having the lowest serum Ig concentrations and the lowest total peripheral blood B cell counts. In contrast, CD70 and CD134 were normally expressed on in vitro activated T cells. CD134L was not detected on patient and control B cells in our activation conditions. Functional studies of in vitro Ig production demonstrated an absence of B cell response to CD27 cross-linking, in particular in a patient with normal CD27 expression. Our results indicate that a defect in CD27 expression or function contributes to the pathogenesis of certain severe forms of CVID.

To clarify the different anti-CD26 mAbs corresponding different functions of CD26, the correlation of the epitopes defined by anti-CD26 mAbs and the functions of CD26 have been studied. Using truncated, human--rat CD26 swap mutants and cross-blocking studies, 13 anti-CD26 mAbs were divided into 5 separate groups. These 5 epitopes were localized between the 1-247th, 248-358th, 359-449th (closer to the 359th amino acid), 450-577th and 359-653th amino acid regions. MAbs against two of these five epitopes, the 248-358th and 359-449th amino acid regions, were associated with inducing modulation of CD26 and T-cell costimulation through the CD3 pathway. Furthermore, mAbs against one of these epitopes, the 359-449th amino acid region, appeared to encompass the ADA binding domain. Analysing the avidity of each mAb to the CD26 molecule using DPPIV enzymatic activity as an indicator, we found that the function of CD26 had little correlation with the avidity of anti-CD26 mAbs, suggesting that distinct epitopes defined by anti-CD26 mAbs appeared to be associated with different functions of CD26. These results will be very useful in the further definition of the functional domains of CD26.

Hematologic engraftment and immune reconstitution were examined in patients who received cyclophosphamide and total body irradiation therapy followed by infusion of autologous bone marrow purged with anti-B1 monoclonal antibody (MoAb) and complement as therapy for non-Hodg-kin' 's lymphoma. Hematologic engraftment was prompt with return of ≥ 0.5 × 103/µl granulocytes and ≥ 2 × 104/µL platelets at a median of 26 and 29 days posttrans-lant, respectively. Immunologic reconstitution, in contrast, was prolonged. Normal numbers of circulating B cells were consistently noted by five months posttransplant, whereas return of normal immunoglobulin levels in some patients did not occur for one year. Normal numbers of T cells were evident within the first month posttransplant, but a reversed T4:T8 ratio persisted in some patients up to three years. In vitro responses of either B cells to triggers of activation or of T cells to mitogens and antigens were not normal for at least three months posttransplant. Natural killer (NK) cells predominated early after transplant and may demonstrate cytotoxicity against tumor cells. Our studies demonstrate that transplantation with anti-B1 purged autologous bone marrow results in complete hematologic and delayed immunologic engraftment. No significant acute or chronic clinical toxicities have been observed. © 1987 by Grune & Stratton, Inc.