Experimental myocarditis: in vitro and in vivo studies of lymphocytes sensitized to heart extracts and group A streptococci

Cytotoxicity was found in 78 per cent of rat heart cell cultures in contact with lymphocytes sensitized to rabbit heart extracts and in 65 per cent of those exposed to lymphocytes sensitized to rat heart. Lymphocytes sensitized to group A streptococci were cytotoxic on 82 per cent of the cultures while controls were affected in less than 20 per cent and to a much more limited extent. Agglutination of the sensitized lymphocytes by antilymphocytic serum inhibited the cytotoxic effect.

Passive transfer of lymphocytes from Lewis rats sensitized to rabbit heart produced myocarditis in thirteen of fourteen rats. The significance of these findings is discussed in relation to the pathogenesis of experimental myocarditis.

Effect of repeated isoproterenol administration in young rats. A histological and serological study

Young rats were injected repeatedly with large doses of isoproterenol either daily for 3 days or once weekly for 2, 3 and 4 weeks, and sacrificed at different time intervals. The histological changes in the myocardium were described and compared with those found in rats given single doses of the drug. Rats sacrificed one week or more after isoproterenol injections showed focal cellular myocardial lesions. The possible mechanisms of their production is discussed. Serological examinations were performed by the haemagglutination method and no circulating anti-heart antibodies were detected.

The relationship between lymphocyte transformation and immune responses. II. Correlations between transformation and humoral and cellular immune responses

Rabbits were immunized against purified proteins, tissue extracts or sheep erythrocytes, with or without Freund's adjuvant. Skin reactions of the delayed type were found only in animals given antigen with adjuvant, although all rabbits developed serum antibodies and most of them Arthus type reactions. Lymphocytes of all animals, however, showed similar transformation activity when cultured with the immunizing antigen.

Thus the blast transformation phenomenon correlates well with both cellular and humoral immune responses and not with the delayed type hypersensitivity only.

Studies on lysosomes in rat heart cell cultures. I. The effect of lysosomal labilizers

Lysosomal labilizers including vitamin A acid and alcohol, chlorpromazin (CPZ) and dimethylsulfoxide (DMSO) caused damage to rat heart and kidney cell cultures by a primary effect on the cell membrane and not on the lysosomes. Intact lysosomes could be observed even in very late stages of cell destruction produced by vitamin A. CPZ 10^-3 M and 25 per cent DMSO caused disruption of the cell membranes including the lysosomes after 5-60 min. The significance of the surface activity of the material used in the cell damage is stressed.

The relationship between lymphocyte transformation and immune response

A comparison was made between the number of cells forming or carrying antibody and those stimulated to transform in vitro by antigen, by using blood lymphocytes from rabbits immunized against sheep erythrocytes.

In blood samples collected 7–77 days after a single immunization, the number of transformed cells was always markedly higher than that of cells forming plaques or rosettes.

It is suggested that unsensitized cells are induced to transform by a stimulus transferred from other reacting cells.

Transformation of lymphocytes from patients with rheumatic fever by streptolysin S

Lymphocytes from peripheral blood were tested for blast transformation reaction by streptolysin S (SLS), phytohaemagglutinin (PHA) and staphylococcal filtrate (SF). The subjects comprised twenty-eight patients with acute rheumatic fever, twenty-seven with other diseases and eight normal donors. The degree of transformation stimulated by SLS was markedly lower in most patients with acute rheumatic fever than in the other groups. On the other hand, all subjects reacted similarly to PHA and SF. The degree of blast formation induced by SLS was changed in many cases when the calf serum in the test medium was substituted by autologous plasma.

The value of the reaction to SLS as a possible diagnostic test for acute rheumatic fever is limited as some patients with acute rheumatic fever react normally while some patients with other diseases show a diminished response.

Spontaneous and experimental myocarditis: the effect of Freund's adjuvant on the heart and other organs

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Isoproterenol induced myocardial lesions in the immunized and non-immunized rat. II. Histopathological lesions after specific immunization

Rats killed 24 hours after a single injection of 30–100 mg/kg Isoproterenol (N-iso-propyl noradrenaline), show focal myocardial necrosis. Animals previously immunized against homologous (rat) heart homogenate showed a marked increase in severity and extent of the lesions. Immunization against rabbit heart caused a lesser degree of enhancement; rat kidney, rabbit serum and kidney and saline—adjuvant emulsion as antigens, gave results similar to the controls.

There was no correlation between the level of circulating anti-heart antibodies, as measured by passive haemagglutination, and the severity of the myocardial necrosis. Within each treatment group, however, animals with higher titres tended to show greater myocardial damage.

It is suggested that circulating anti-heart antibodies, normally non-toxic in vivo, become cytopathogenic after the myofibre cell barrier is broken down by Isoproterenol.