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The cross-reactivity of heterologous erythrocytes was measured at the level of the B and the T cell. B cells produced antibody with restricted cross-reactivity as compared with the cross-reactivity of T cells, assayed by their ability to help B cells in a primary anti-sheep erythrocyte immune response. Helper function was maximally elicited with low antigen doses. The data suggest that the T-cell antigen receptors for erythrocyte antigens differ in specificity from those of B cells and that the sensitivity of T cells to antigen may be very great. [ABSTRACT FROM AUTHOR]

The results suggest that the anaemia in mice associated with the injection of C. parvum is mediated by an immune mechanism. Survival studies of 51Cr-labelled red blood cells (RBC) in splenectomized and unsplenectomized mice show that mice immunized with C. parvum three times, clear RBC faster than unimmunized mice. However, hyperimmunized mice stabilized their haemoglobin concentrations above their minimum level and did not clear 51Cr-labelled RBC faster than unimmunized mice. All mice produced antibody against C. parvum but remained direct Coombs'-negative. Serum from immunized animals did not contain opsonins for -51Cr-labelled RBC. The reticulocytosis, normal osmotic fragility tests and normal survival times of 51Cr-labelled RBC from C. parvum-immunized mice all suggest that the main direct influence of the micro-organism is extrinsic of the RBC. Antigens from the micro-organism were adsorbed by erythrocytes in vitro. It is hypothesized that the anaemia is caused by destruction of RBC brought about by antibody reacting with bacteria that have been adsorbed by RBC. [ABSTRACT FROM AUTHOR]

The effect of procarbazine and cyclophosphamide on the formation of antibodies to sheep red blood cells in mice is investigated. Cyclophosphamide was found to have the best immunosuppressive effect when given after antigen; recovery from drug treatment was relatively fast; under experimental conditions that favour cyclophosphamide action (antigen prior to drug) IgM formation was found to be depressed and prolonged; IgG formation was markedly depressed or altogether missing. Procarbazine was found to act best when given prior to antigen; recovery was slow; under experimental conditions that favour procarbazine action (drug prior to antigen) the induction period was prolonged. IgM titres were slightly and IgG titres markedly depressed. Under all conditions tested procarbazine had little effect on the onset of IgG production. [ABSTRACT FROM AUTHOR]

Naturally occurring titres of heterophil haemagglutinins against rat erythrocytes are related to ABO blood groups, being higher in people of blood groups O and A and lower in people of blood groups B and AB. Comparable titres of haemagglutinin activity can be demonstrated against human AB erythrocytes as well as rat erythrocytes. Activity against rat erythrocytes can be absorbed with human AB erythrocytes and vice versa. Furthermore, after absorption of heterophil antibody with human A or B erythrocytes, heat elution allows partial recovery of the antibody which reacts with rat erythrocytes. A rise in titre of heterophil antibody comparable to that occurring after renal transplantation was demonstrated after surgical operations but only where blood transfusions were given. It is postulated that these rises in antibody titre result from exposure to non-HL-A isoantigens which crossreact with human A and B substance and rat erythrocyte antigens. These antibodies can be distinguished from Forsmann and infectious mononucleosis antibodies, are absent in placental cord blood, occur naturally as IgM and respond to a secondary challenge as IgG, except in immunosuppressed renal transplant patients, where both IgG and IgM responses occur. [ABSTRACT FROM AUTHOR]

A significant increase in titre of human heterophil antibodies against rat erythrocytes was demonstrated in eighteen of twenty-eight patients after renal transplantation. Although this rise in titre preceded an acute rejection episode in the renal graft in some instances, it is considered that this relationship was coincidental. There is no relationship between the numbers of such rejection episodes or the degree of incompatibility for HL-A antigens between donor and recipient and the titres of heterophil antibodies after transplantation. [ABSTRACT FROM AUTHOR]

Homocytotropic antibody induced with ragweed and timothy pollen extract has been produced in non-atopic dogs. Characterization of the antibody was carried out by direct skin tests, passive transfer, tanned red cell haemagglutination, Sephadex filtration and immunoelectrophoresis. Two types of antibody were induced. A 7S antibody which had skin sensitizing characteristics and a 19S antibody which was the haemagglutinating antibody and 2ME sensitive. The findings are similar to that seen in spontaneous canine atopy except that the dogs did not respond with respiratory or systemic symptoms after antigenic challenge. [ABSTRACT FROM AUTHOR]