Variable inotropic effect of immune cells on mice atria--participation of metabolic products of arachidonic acid.

The effect of BALB/c anti CF1 lymph node cells and thymocytes on the spontaneous activity of isolated CF1 mouse atria was studied. Immune lymph node cells induced opposite effects depending on the number of immunizations. Immune lymph node cells from mice which received two immunizations decreased the contractile tension of the atrium, whereas, cells from mice exposed to three and five immunizations strongly increased the tension. Immune thymocytes induced only negative inotropic action and this effect did not depend on the number of immunizations. Indeed, it was similar after two, three or five immunizations. Control normal lymph node cells or thymocytes from BALB/c or CF1 mice had no effect on CF1 atria. Furthermore, BALB/c anti CF1 cells had no effect on BALB/c atria. Inhibitors of cyclooxygenase activity prevented the negative inotropic influence of immune thymocytes and lymph node cells seen after two immunizations. In contrast, inhibitors of the lipoxygenase pathway abolished the positive inotropic action induced by lymph node cells obtained after three and five immunizations. Cell-free supernatants of lymph node cells from animals receiving five immunizations, stimulated the contractile activity of atrium, while those from thymocytes inhibited it, indicating that soluble factors are generated by contact of immune cells with the myocardium. It is proposed that upon recognition of alloantigens expressed by atrial cells, lymph node cells and thymocytes are activated and release either arachidonic acid metabolites or some factor(s) that induces this release by other cells, which in turn triggers different effects in myocardial tissue depending on the set of cells involved in the primary immune response.