IgG antibodies to neutrophil polymorphonuclear cells (PMNs) were detected by a simple indirect immunofluorescence method that did not require chemical or enzymatic modification of the cells. Based on recent information about the human PMN Fc gamma-receptor, nonspecific binding of IgG to PMNs was virtually completely prevented by incubating cells at 37 degrees C with human serum diluted 1 to 3 in the presence of a high concentration of rabbit IgG. This also facilitated distinction of sera with weak anti-PMN activity from normal sera. On the other hand, nonspecific staining remained on a fraction (10-25%) of mononuclear leukocytes. Following first-time transfusion of 0.5 to 5 units of whole blood or red cell concentrate, 4 of 27 patients (15%) developed anti-leukocyte antibodies. Anti-leukocyte antibodies were detected in 51 percent of 47 patients with reported febrile transfusion reactions; the IgG antibodies bound to PMNs in 38 percent of these 47 patients. Since only about one in three patients with febrile transfusion reactions had detectable IgG anti-PMN antibodies, fever may be caused by lysis of leukocytes other than PMNs.

ABO Blood-Group System↗

PubMedDate not supplied

Minimal expression of blood group A antigen on thrombocytes from A2 individuals.

Two multiply transfused group O patients developed refractoriness to random-donor platelet transfusions. Both had high-titer IgG antibodies to group A and B antigens. Subsequent transfusions with ABO-compatible platelets were successful, suggesting that the ABO blood group system is significant in the development of refractoriness to platelet transfusions. By indirect immunofluorescence, the patients' IgG anti-A reacted with platelets from group A1 donors but not with those from group A2 donors. A2 platelets were at least 38 times less efficient at adsorbing a mouse monoclonal anti-A; the difference between the adsorbence capacities of A2 and O platelets was minimal. Transfusion of A2 platelets, unlike that of A1 platelets, effected a good increment in the platelet counts of these two patients. The results indicate that the expression of A2 antigen on platelets from A2 subjects is minimal.

ABO Blood-Group System↗

PubMedDate not supplied

Antinucleosome autoantibodies bind directly to cell lines in vitro and via the FcgammaRIIB receptor to B lymphocytes in vivo: a role for immune complexes in interactions between antinucleosome IgG2a and B cells of BXSB lupus mice.

The initial novel observation of this study was that most B cells of male BXSB lupus mice bear surface IgG2a(b) of extrinsic origin. To define the surface antigen, we here examine three (NZBxBXSB)F1-derived IgG2a(b) monoclonal antibodies (mAbs) selected for binding to cell surfaces. Surprisingly, all three mAbs bound the nucleosome (nuc) particle, the fundamental unit of chromatin and an early target of autoimmunity in systemic lupus erythematosus. Their tentative dissociation constant (K(d)) for soluble nuc particles was approximately 7 x 10(-10) m. The mAbs bound more weakly to both H2A-H2B-DNA and H3-H4-DNA complexes, and in immunoblot they stained all four core histones. The mAbs detected a surface antigen on all cell lines examined, present on viable cells. When stripped of nuc, and in the presence of DNase I, their binding to cell lines improved. Heparin displaced the antigen from the cell surface. In vivo, the three mAbs stained B cells of several BALB/c mice clearly stronger than the isotype control; this differential staining was significantly reduced in FcgammaRIIB-deficient mice. The results indicate that the three mAbs recognize (a) planted antigen on viable cultured cells and (b) soluble autoantigen in vivo, leading to immune complexes that bind to FcgammaRIIB. Further experiments demonstrated that antinuc IgG2a could be eluted from splenocytes of a male BXSB lupus mouse. Hence, at least part of the extrinsic IgG2a(b) found on BXSB B cells may represent FcgammaRIIB-bound nuc-IgG2a(b) complexes.

Animals↗