Elevated thymocyte norepinephrine and cyclic guanosine 3',5' monophosphate in T-lymphocytes from exercised mice with coxsackievirus B3 myocarditis

Methyl mercury exposure via placenta and milk impairs natural killer (NK) cell function in newborn rats

The effect of methyl mercury (MeHg) exposure (3.9 micrograms/g diet) on the development of immune function was studied in the newborn Sprague-Dawley rat after MeHg exposure via placenta and/or milk. No consistent alterations were observed between control and treated offspring (at the age of 15 days) on the following parameters: body weights, lymphoid organ weights or cell number, and the lymphoproliferative response to B-cell mitogen. The lymphoproliferative response to T-cell mitogen was increased in thymocytes (by 30-48%), but decreased in splenocytes (by 30-32%). This decreased activity was only observed in the groups exposed during lactation. White blood cell counts (WBC) were increased in all groups. Natural killer (NK) cell activity was reduced (by 42%, P less than 0.01) in the group that was exposed both via placenta and milk. These results indicate that placental and lactational transfer of MeHg does adversely affect the developing immune system of the rat.

Effects of methyl mercury exposure on spleen and blood natural killer (NK) cell activity in the mouse

The effect of 12 weeks of exposure to methyl mercury (MeHg) (3.9 micrograms/g diet) on the immune function was studied in female Balb/c mice. This MeHg dose did not affect body, kidney, liver or spleen weight. Thymus weight and cell number decreased by 22% (P less than 0.05) and 50% (P less than 0.001), respectively. The lymphoproliferative response to T and B cell mitogens, however, tended to increase in both lymphoid organs. Natural killer cell activity was reduced by 44% (P less than 0.01) and 75% (P less than 0.05) in the spleen and blood, respectively. The number of red blood cells increased slightly (12%, P less than 0.05), whereas white blood cell counts were unaffected. These results indicate that MeHg evokes immune suppressive effects on protective cytotoxic capacity that is of major importance in the pathogenesis of several diseases.

Exercise in coxsackie B3 myocarditis: effects on heart lymphocyte subpopulations and the inflammatory reaction

To investigate whether exercise in coxsackie B3 virus infection is detrimental to the myocardium, Balb/c mice were inoculated with the virus and exercised to exhaustion on a motor-driven treadmill up to 48 hours after the inoculation. This infection evokes myocarditis. The inflammatory and necrotic lesions in the ventricular myocardium 7 days after the inoculation covered 4.32% of the tissue section area in the nonexercised group. Exercise at 0 hours did not affect this myocardial damage (4.77%), whereas exercise at 48 hours after the inoculation increased the lesion to 7.85% (p less than 0.05). Lethality was not influenced by exercise. The response pattern of myocardial lymphocyte subpopulations was studied with an immune histochemical staining technique. The number of T cytotoxic, T suppressor cells increased threefold (p less than 0.01), and the T cytotoxic, suppressor/T helper cell ratio increased twofold (p less than 0.01) with exercise at 48 hours but was unchanged with exercise at 0 hours. The number of class II expressing cells decreased with exercise at 48 hours (p less than 0.05) and was negatively correlated (p less than 0.01) with the size of the inflammatory reaction. The development of myocardial inflammatory and necrotic lesions seems to be dependent on the presence and cooperation of class II expressing cells and T killer cells. Furthermore, failure to restrict physical activity in the acute phase of this infection may well contribute to the progression of the disease.