To characterize cell surface molecules involved in control of growth of malignant lymphocytes, monoclonal antibodies were raised against the human B lymphoblast cell line SKW6.4. One monoclonal antibody, anti-APO-1, reacted with a 52-kilodalton antigen (APO-1) on a set of activated human lymphocytes, on malignant human lymphocyte lines, and on some patient-derived leukemic cells. Nanogram quantities of anti-APO-l completely blocked proliferation of cells bearing APO- polyacrylamide gel electrophoresis (SDS-PAGE) as a main band of 52 kD (Fig. 1). Apart from actin (43 kD), which was nonspecifically precipitated with IgG3, anti-APO-1 specifically immunoprecipitated a minor band of 25 kD. This 25-kD protein might either represent a degradation product or be noncovalently associated with the 52-kD protein.There are two major modes of death in nucleated eukaryotic cells. Necrosis as a result, for example, of complement attack is characterized by swelling of the cells and rupture of the plasma membrane caused by an increase in permeability. Cells that undergo apoptosis, however, show a different biochemical and morphological pattern (2). This pattern corresponds to the one induced by anti-APO-1: condensation of the cytoplasm, membrane blebbing (Fig. 2a) (1988). 18. DNA fragments without GREs were inserted into the Xba I site (see Fig. 2) of -33 GRE6, displacing the GRE cassette to -262, -366, and -1069 bp from the start of transcription. Weak receptor-mediated activation was detected when GREs were situated at -262, but no effect was observed from the more distal sites.

Splenectomized and asplenic patients have a high incidence of infections by encapsulated bacteria and do not respond to polysaccharide vaccines. To understand whether the absence of the spleen is associated with a defined B cell defect, we analyzed B cell subsets in the peripheral blood. We found that a population of B cells known as immunoglobulin (Ig)M memory is lacking in patients without spleen. The absence of IgM memory B cells correlates with an impaired immune response to encapsulated bacteria not only in splenectomized patients, but also in individuals with an intact spleen. We show that the physiological and transient predisposition to pneumococcal infections of young children (0–2 yr) is associated with the lack of circulating IgM memory B cells and of serum antipolysaccharide IgM. We also demonstrate that IgM memory B cells are undetectable in a fraction of patients with common variable immunodeficiency, who have recurrent and invasive infections by encapsulated bacteria. IgM memory B cells, therefore, require the spleen for their generation and/or survival and are responsible for the protection against encapsulated bacteria.

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stem cell transplantation (HSCT) in patients with severe presentation of LPS-responsive beige-like anchor protein (LRBA) deficiency, but long-term follow-up and survival data beyond previous patient reports or meta-reviews are scarce for those patients who do not receive a transplant. Objective: This international retrospective study was conducted to elucidate the longitudinal clinical course of patients with LRBA deficiency who do and do not receive a transplant. Method: We assessed disease burden and treatment responses with a specially developed immune deficiency and dysregulation activity score, reflecting the sum and severity of organ involvement and infections, days of hospitalization, supportive care requirements, and performance indices. Results: Of 76 patients with LRBA deficiency from 29 centers (median follow-up, 10 years; range, 1-52), 24 underwent HSCT from 2005 to 2019. The overall survival rate after HSCT (median follow-up, 20 months) was 70.8% (17 of 24 patients); all deaths were due to nonspecific, early, transplant-related mortality. Currently, 82.7% of patients who did not receive a transplant (43 of 52; age range, 3-69 years) are alive. Of 17 HSCT survivors, 7 are in complete remission and 5 are in good partial remission without treatment (together, 12 of 17 [70.6%]). In contrast, only 5 of 43 patients who did not receive a transplant (11.6%) are without immunosuppression. Immune deficiency and dysregulation activity scores were significantly lower in patients who survived HSCT than in those receiving conventional treatment (P 5 .005) or in patients who received abatacept or sirolimus as compared with other therapies, and in patients with residual LRBA expression. Higher disease burden, longer duration before HSCT, and lung involvement were associated with poor outcome. Conclusion: The lifelong disease activity, implying a need for immunosuppression and risk of malignancy, must be weighed against the risks of HSCT.

Abnormal processing of immune complexes (IC) may be important in the pathogenesis of systemic lupus erythematosus (SLE). The clearance of large soluble IC (comprising hepatitis B surface antigen (HBsAg)/anti-HBsAg) radiolabeled with "23I was examined in 12 normal subjects and 10 patients with SLE. IC localization was analyzed by static and dynamic gamma-scintigraphy. Initial IC clearance from blood was more rapid in patients (median 11/2 = 2.15 min) than normals (median t1/2 = 5.15 min) due to more rapid uptake in the liver. However, in the SLE group, up to 12% of complexes were released from the liver after 30-50 min. Splenic uptake of immune complexes was reduced in the patients and there was reduced ability to retain IC in this organ. Plasma complement levels and erythrocyte complement receptor type 1 numbers were reduced in the patients, resulting in defective opsonization of IC and reduced red cell binding in vivo. These observations support the hypothesis that IC handling is abnormal in SLE. (J. Clin.

DNA ligase IV (LigIV) deficiency was identified as the molecular basis for a severe form of combined immunodeficiency in two microcephalic siblings with cellular radiosensitivity. In one patient the diagnosis was made directly after birth, allowing analysis of the role of LigIV in the development of specific immune cells. Absolute numbers of B cells were reduced 100-fold and αβ T cells 10-fold, whereas γδ T cells were normal. Spectratyping of all three cell populations showed a diverse repertoire, but sequencing of IgH V(D)J junctions revealed shorter CDR3 regions due to more extensive nucleotide deletions among D and J elements and fewer N nucleotide insertions. Clonal restriction of IgG-expressing, but not IgM-expressing, B cells and the lack of primary and secondary lymph node follicles indicated impaired class switch recombination. Observations in the older sibling showed that this rudimentary immune system was able to mount specific responses to infection. However, partial Ab responses and extensive amplification of γδ T cells could not prevent a life-threatening course of viral and bacterial infections, the development of an EBV-induced lymphoma, and immune dysregulation reflected by severe autoimmune cytopenia. Impaired generation of immune diversity under conditions of limited LigIV activity can cause a human SCID variant with a characteristic immunological phenotype.

We describe a method to facilitate radioimaging with technetium-99m (99mTc) by genetic incorporation of a 99mTc chelation site in recombinant single-chain Fv (sFv) antibody proteins. This method relies on fusion of the sFv C terminus with a Gly4Cys peptide that specifically coordinates 99mTc. By using analogues of the 26-10 anti-digoxin sFv as our primary model, we find that addition of the chelate peptide, to form 26-10-1 sFv', does not alter the antigen-binding affinity of sFv. We have demonstrated nearly quantitative chelation of 0.5-50 mCi of 99mTc per mg of 26-10-1 sFv' (1 Ci = 37 GBq). These 99mTc-labeled sFv' complexes are highly stable to challenge with saline buffers, plasma, or diethylenetriaminepentaacetic acid. We find that the 99mTc-labeled 741F8-1 sFv', specific for the c-erbB-2 tumor-associated antigen, is effective in imaging human ovarian carcinoma in a scid mouse tumor xenograft model. This fusion chelate methodology should be applicable to diagnostic imaging with 99mTc and radioimmunotherapy with 186Re or 188Re, and its use could extend beyond the sFv' to other engineered antibodies, recombinant proteins, and synthetic peptides.

and IWT-TBM (ZL36300700). I.M. is supported by a Klinisch onderzoeksfonds (KOF) mandate of the KU Leuven, Belgium. Disclosure of potential conflict of interest: G. Frans personally received a GOA grant from KU Leuven and support for travel from Academische Stichting Leuven and Fonds Wetenschappelijk Onderzoek (FWO) for this work. I. Meyts' institution received a grant from Shire-CSL Behring for other works and travel expenses from Octapharma-Gilead. X. Bossuyt personally received the GOA grant from KU Leuven for this work. The rest of the authors declare that they have no relevant conflicts of interest.