Modulation of the H-2 antigenicity on the surface of murine peritoneal cells

Lung injury mediated by antibodies to endothelium. I. In the rabbit a repeated interaction of heterologous anti-angiotensin-converting enzyme antibodies with alveolar endothelium results in resistance to immune injury through antigenic modulation

To study the effects of relatively long-term interaction of antibodies with surface antigens of lung endothelium, rabbits were intravenously injected for a maximum of 4 d with goat anti-rabbit lung angiotensin-converting enzyme (Gt anti-RbACE) antibodies. On day 1 69%, on day 2 13%, and on days 3 and 4 of injection none of the rabbits developed lethal pulmonary edema. By immunofluorescence microscopy, deposits of GtIgG, frequently in association with RbC3, were found along the endothelium of alveolar capillary walls in all rabbits studied on day 1, in 57% on day 2, in 33% on day 3, and in none of them on day 4. While in vitro anti-ACE antibodies bound in a linear pattern to the lung endothelium, the binding pattern in vivo was distinctly granular. The in vivo interaction of antibodies with ACE also redistributed ACE in a granular pattern along capillary walls. In contrast to the granular deposition of injected anti-ACE IgG and F(ab')2 fragments of anti-ACE IgG, Fab fragments of anti-ACE IgG localized, without fixing C3, in a linear pattern along the endothelium of lung capillaries and did not modify the normal distribution of ACE. However, when the injection of Fab fragments of Gt anti-RbACE IgG was followed by an injection of Rb anti-GtIgG serum, granular deposits of Gt Fab fragments, RbIgG and RbC3 were seen along alveolar capillary walls. Biochemical measurement of ACE activity in lung homogenates provided data in agreement with those obtained by immunofluorescence microscopy, showing diminished activity to none on day 4, with some return of ACE activity on day 5, 24 h after the last injection of antibody, and normal values on day 21. The results obtained indicate that divalent antibodies to an antigen expressed on the plasma membrane of rabbit lung endothelial cells promotes a rapid redistribution of antigenic receptors, fixation of complement and, in surviving rabbits, disappearance of the antigen from the endothelial cells that are no longer susceptible to immune injury. In vivo "immunologic enzymectomy" induced by a ligand-surface antigen interaction is an example of antigenic modulation. These events may have an important role in the pathogenesis of inflammatory lesions induced by antibodies reacting with antigens expressed on the plasma membrane of cells in the lung and in other organs.

Preparation and properties of antisera to Mph-1, the mouse macrophage alloantigen

Mph-1 is an alloantigen demonstrable on mouse peritoneal macrophages. Two lines, B10M.I and C.I, have been bred for use with strains I/StDa or BALB/c to produce appropriate alloantisera. Optimal immunization procedures for production of anti-Mph-1.2 (the common antigen) are described. Antisera against Mph-1.1 have so far been obtained only erratically. Antisera show complement dependent cytotoxicity against normal peritoneal macrophages and cultured blood monocytes but have no obvious effect on peritoneal lymphocytes or cultured blood neutrophils. Absorption studies show that cell for cell normal peritoneum has about fifteen times more antigen than lymph node, spleen, liver or bone marrow and at least eighty times more than thymus. We were unable to use the antiserum to cause passive enhancement of skin grafts in mice.

IgG-binding sites on macrophage cell membrane. II. Mobility of Fc receptors induced by the interaction with their corresponding IgG ligands

Mouse peritoneal macrophages were charged with IgG molecules in monomeric (mIgG), heat-aggregated (agIgG) or antigen-complexed (acIgG) form. Upon exposure to 37 degrees C, all bound IgG ligand types are redistributed on the cell surface due to the mobilization of their corresponding Fc receptor (FcR). The major findings regarding the fate of FcR on macrophages bearing IgG ligands are as follows: (a) the FcR involved in the binding of cytophilic molecules has a slow movement on the cell membrane and forms patches but never caps, while the opsonic type of FcR is rapidly capped; (b) the mobility of IgG-binding sites was temperature-dependent and was affected differently by sodium azide; this metabolic inhibitor enhances the disappearance of mIgG from the cell surface but decreases the capping and the disappearance of polymeric ligands; (c) both FcR types are probably ingested when complexed with specific ligand, and consequently, the rebinding of homologous IgG molecules is reduced, the clearing induced by agIgG or acIgG binding being much more extensive; and (d) cells cleared of their opsonic types of FcR are able to regenerate the receptor molecules with 8 h of incubation at 37 degrees C.

Immunologic induction of reticulum cell sarcoma: donor-type lymphomas in the graft-versus-host model

The aim of this study was to investigate malignant lymphomas of donor origin induced in F1 mice undergoing a chronic graft-versus-host reaction (GVHR) after injection of parental strain spleen cells. A total of 3 X 10(8) or 4 X 10(8) C57BL/10 spleen cells were administered to 7-8-week-old H-2 incompatible (C57BL/10 X HTG)F1 hybrids either as single or fractionated i.p. injections. Recipients were killed at intervals ranging from 1 month to 1 year after the first injection and their lymphoid cells typed for host-derived and donor-derived histocompatibility antigens. In 49% of the 88 GVH F1 mice, cells failed to be killed by a hyperimmune serum against HTG (H-2g) but reacted normally with antisera to C57BL/10 (H-2b) and, in the 9 cases tested, to theta-C3H. The conclusion that the lymphoid cells of these mice were derived from donor cells was supported by the finding that these animals lacked immunoglobulins bearing host-derived Iga allotype in their serum. Forty-three percent of the GVH F1 mice developed reticulum cell sarcomas (RCS), 32% revealed hyperplastic lymphoreticular tissue, and 25% showed no grossly abnormal changes. Mice with donor-type lymphoid tissues were found in all three groups; 50% of the 38 RCS detected were donor-type neoplasms. The induction of donor-type RCS during the GVHR strengthens the concept of lymphomagenesis through persistent stimulation with antigen(s).

Phenotypic variations with time of some HL-A antigens

In order to study the HL-A antigen turnover in vivo, the HL-A reactivities of the lymphocytes of eight blood donors were tested every week for six weeks with antisera HL-A1, 2, 3, 5, 7, 8 and 11. The analysis of variance showed that the "time" effect and the "time times donors" interaction were statistically significant for the HL-2, 3, 5 and 11 specificities. This supports the hypothesis that phenotypic expression of such antigens on the lymphocyte membrane of some of the blood donors examined varied with time. From a practical point of view, the HL-A antigenic fluctuation with time should be taken into consideration when lymphocyte typing is required for tissue transplantation.

Immunologic injury in measles virus infection. II. Suppression of immune injury through antigenic modulation

Upon the addition of antibody to measles virus, measles virus antigens expressed on the surface of infected cells can be modulated from the cell's membrane in vitro. Removal of measles virus antigens from the surface of cells occurs relatively rapidly and is accompanied by a parallel reduction in the ability of antibody and complement to lyse these cells. Modulation of surface viral antigens can occur in the absence of cap formation and is fully reversible once measles virus antibodies are removed from culture medium. Protracted exposure of acutely infected cells to measles virus antibodies results in a population of cells that exhibit normal cytomorphology and growth behavior. These cells continue to express measles virus antigens internally, but not at the cell surface, and are refractory to immune lysis. Once antiviral antibody is removed, measles virus antigens again appear on the cell surface, giant cell and syncytial formation occur, and cell death follows. These observations may explain the persistence of virus in spite of a vigorous host antiviral immune response in certain chronic infections of man.

The association of H-2 antigens and EAC receptors on the surface of peritoneal cells

The exposure of murine peritoneal cells to anti-H-2 sera results in a diminished expression of H-2 antigen on the cell surface. Concomitant with this "H-2 modulation" the capacity of macrophages to bind sheep red blood cells coated with antibody and complement (EAC) was markedly diminished. In contrast, there was no change in the capacity of modulated macrophages to bind sheep red blood cells coated with antibody alone (EA). Antibodies to K end H-2 specificities were more effective in reducing the binding of EAC than antibodies to D end H-2 specificities. Exposure of peritoneal cells to O or Ly antisera had no effect on the formation of EAC rosettes. Exposure of peritoneal cells to anti-H-2 sera, under conditions which would not allow modulation of H-2 antigens, also prevented the reduction of EAC binding. Thus, the EAC receptors and H-2 antigenic specificities seem to be closely related on the surface of peritoneal cells, but constitute distinct cell surface structures. Preliminary evidence indicates that vinblastine, a microtubule depolymerizing agent, may disrupt the close association of EAC receptors and H-2 antigens. It is suggested that the association of EAC receptors and K end H-2 determinants on the membrane of macrophages may have implications for the regulation of the immune response by H-2-linked Ir genes.