Characterization of surface alloantigens of murine neutrophils

The presence of blood group and lymphocyte antigens on porcine granulocytes

Suspensions of highly viable (less than 95%) granulocytes minimally contaminated by other cell types were isolated from the peripheral blood of pigs by a single centrifugation with low molecular weight dextran and after preferential lysis of erythrocytes by hypotonic shock. A complement-dependent cytotoxic test showed the presence of antigens of the SLA major histocompatibility complex, the SLB leucocyte system and the A and E blood group systems on the granulocytes. Some SLA typing reagents against class I (SD) antigens did not react with granulocytes, however, or yielded dubious reactions. The findings showed that the reactivity of SLA sera resembles the reactivity fo human HLA sera. The results also show that compatibility in the SLA, SLB, A and E systems will have to be taken into account when preparing alloimmune sera for the determination of granulocyte-specific antigens of pigs.

The cell surface phenotype of mouse neutrophils

Using monoclonal antibodies, mouse peritoneal neutrophils were typed for the presence of 23 cell surface alloantigens, the expression of which was quantitated by flow cytofluorometry and compared with that of lymphocytes. The H-2K and H-2D alloantigens and beta 2-microglobulin were present on all neutrophils, but Ia and Qa antigens were not detected. It was found that Ly-5.1, Ly-15.2, Ly-21.2, Ly-24.2 (Pgp-1) and Ly-25.1 were present on greater than 90% of neutropils; Ly-6.2 and Ly-27.2 were absent, but Ly-28.2 (encoded by an Ly-6 linked gene), was present on greater than 90% of neutrophils. As expected, the lymphocyte-specific antigens Ly-1.1, Ly-2.2, Ly-3.1, Ly-7.2, Ly-12.1 and Thy-1.2 were absent from the neutrophils. When compared with lymphocytes, marked differences in alloantigen expression on neutrophils were seen for Ly-5.1, Ly-24.2 and Ly-28.2. These studies should be of value in the study of neutrophil structure and function.

Gm-3.2, a new granulocyte/macrophage alloantigen

A monoclonal antibody defining a unique mouse neutrophil cell-surface antigen, Gm-3.2, is described. Gm-3.2 is found on all neutrophils in peritoneal exudates and in bone marrow, and is also present on macrophages activated by thioglycolate but is absent from lymphoid, kidney, liver, heart, and red cells. Gm-3.2 is a differentiation antigen of myeloid cells, as granulocyte/macrophage colony-forming cells are Gm-3.2- while mature neutrophils are Gm-3.2+. Strain distribution pattern analysis shows linkage of the Gm-3 locus to the Ly-4, B2m, H-3 complex on chromosome 2.

Alloantibody bipolar bridging; a new mechanism of cell surface activation

Bipolar bridging of cellular membrane receptors and epitopes by alloantibodies (Fab bridging the MHC antigens and Fc the Fc receptors) has been shown on a murine mast cell model to be a way of cell signaling and activation. In order to test a possible general significance of this phenomenon, another model was studied, namely guinea pig neutrophils. It was found l(1) that neutrophils from S2, S13 and BIO-AD strains both express class I (B) and class II (Ia) antigens on their surface, as detected by a Prot.A-SRBC rosetting method, after cell incubation with related alloantibodies; (2) that Fc receptors for IgG (Fc gamma R) were specific for IgG2 subclass, as determined by the same rosetting method after binding of preformed immune complexes (IgG1, IgG2 and F(ab')2 anti-DNP-DNP25 BSA); and (3) that specific alloantibodies of IgG2 subclass were able to specifically activate the neutrophil oxidative metabolism as shown by superoxide anion (O2-) release, detected by the luminol-dependent chemiluminescence method. Neither the IgG1 nor F(ab')2 portion were able to trigger O2- release. This demonstrates a second situation of a cell membrane activation through alloantibody bipolar bridging.

High-resolution two-dimensional electrophoretic analysis of acidic, basic and surface proteins of mouse neutrophils

The proteins from murine neutrophils have been examined using isoelectric focusing and non-equilibrium pH gradient electrophoresis in the first dimension and sodium dodecyl sulfate-polyacrylamide electrophoresis as a second dimension. The major protein, actin, dominates the protein profiles and it appears to be one of the few proteins being synthesised rapidly. In the presence of protease inhibitors, neutrophil (a homogeneous, non-dividing cell population) lysates gave extremely reproducible two-dimensional electrophoretic patterns both with Coomassie blue staining (approx. 20 proteins detected) and with fluorography or autoradiography after [35S]methionine biosynthetic labelling (approx. 450 proteins detected between pH 4 and 7). Biosynthetic labelling was more sensitive than protein staining for some components, although the mature neutrophils did not synthesis certain cellular proteins (e.g., granule proteins such as lactoferrin). Surface labelling of neutrophils (as indicated by the absence of 125I associated with actin) yielded more than 20 major 125I-labelled proteins on high-resolution electrophoretic maps. The major 125I-labeled protein (Mr approximately 90 kdalton) focused at the acidic end of the gels near pH 4.1. This protein could also be detected after [35S]methionine biosynthetic labelling. All of the high molecular weight components focused over a broad pH range (0.2 pH units). At lease one of the surface components appeared to consist of several discrete charge entities.