Depletion of radiosensitive leukocytes exacerbates the heart sympathetic denervation and parasitism in experimental Chagas' disease in rats.

The acute phase of the Trypanosoma cruzi infection induces damage of the heart sympathetic nerve terminals in rats. The participation of the radiosensitive leukocytes in this process was assessed in young rats submitted to gamma irradiation 1 day before infection with T. cruzi, Y strain. Gamma irradiation increased the heart noradrenergic denervation evaluated at day 12 of infection by histochemical and electron-microscopic methods. The presence of numerous macrophages with ultrastructural features of activation and a significant rise in the myocardial parasitism suggest the involvement of radioresistant macrophages or parasite factors, or both, on the damage of the nerve terminals.

Ultraviolet radiation decreases the granulomatous response to lepromin in humans.

Ultraviolet radiation (UVR) modulates cellular immunity in humans and experimental animals and can interfere with immune responses against infectious agents in animal models. We used the lepromin reaction, a cell-mediated immune response to antigens of Mycobacterium leprae, to determine whether UVR affects the cellular immune response to an infectious agent in humans. We selected 29 healthy, lepromin-positive contacts of leprosy patients and determined their minimal erythema dose (MED) of UVR. Immediately afterward, each subject was injected with 0.1 ml of lepromin in two areas of the buttocks: one at the site that had received twice the MED of UVR and the other on the contralateral, unirradiated site. The irradiated site was given twice the MED every 4 d for a total of five treatments. One week after the last irradiation, both lepromin reactions were measured and biopsied. The size of the lepromin-induced granulomas was significantly reduced in the irradiated site, as was the number of lymphocytes. Immunohistochemical analysis showed a depletion in the number of infiltrating cells and a lower percentage of T cells, particularly the CD4+ subpopulation, in granulomas formed in UV-irradiated skin. This study demonstrates that local UV irradiation reduces the granulomatous reaction to lepromin in sensitized individuals. These findings are of clinical relevance because of the fundamental role played by the delayed-type hypersensitivity response in defense against intracellular pathogens and because of potential increases in the amount of UVR in sunlight reaching the earth's surface.

Effect of UV light on tumor cell sensitivity to NK and NC cell-mediated lysis.

The effect of UV light irradiation on the immunobiological properties of murine tumor cells was studied. In vitro irradiation of MCA 102 and MCA 105 fibrosarcomas with a short-wavelength UVC light rendered them highly immunogenic and sensitive to natural cell-mediated cytotoxicity (NCMC). Analysis of the effector cells involved in NCMC revealed that UV irradiation stably increased tumor cell sensitivity to both NK and NC cell lysis. Studies of the mechanisms responsible for increased sensitivity to NK cells indicate that UV treatment did not affect tumor-cell recognition by NK cells but increased their susceptibility to NK-derived lytic granules. Augmentation of UV-treated tumor cell sensitivity to NC cell-mediated lysis was found to be due to their increase in sensitivity to the effector-cell-released TNF. In parallel, UV-treated cells showed high sensitivity to human recombinant TNF whereas untreated parental cells were resistant to rTNF. UV irradiation did not affect rTNF binding, internalization and degradation but increased tumor cell vulnerability to TNF-induced DNA fragmentation. Thus, UV light appears as a potent modulator of tumor cell sensitivity to T cell- and natural cell-mediated immunity.

Efecto de las radiaciones electromagnéticas no ionizantes sobre la inmunidad humoral y celular en trabajadores expuestos / Non-ionizating electromagnetic radiations effects upon humoral and cellular inmunity among exposed workess

Se estudian sujetos expuestos ocupacionalmente por más de 10 años a radiaciones electromagnéticas no ionizantes. Se realizaron determinaciones de inmunocomplejos; cuantificación de inmunoglobulinas A, G y M, y prueba de roseta activa y espontánea para estudiar inmunidad humoral y celular, así como otras pruebas. Se utilizó un grupo control con edad promedio similar al grupo estudiado y no expuesto a radiaciones. Se evidenciaron cambios en la inmunidad humoral, dados por alteraciones encontradas en la IgG e IgA. Se comprobó la disminución de la roseta activa y espontánea en el grupo expuesto en relación con el grupo control

Schistosoma mansoni: aspectos quantitativos da fertilidade e sobrevida de vermes oriundos de cercarias irradiadas com 3 KRAD, em camundongos / Schistosoma mansoni: quantitative aspects of the fertility and survival of worms derivated form irradiated cercariae (3KRAD), in mice

Quatro grupos de camundongos albinos (Mus musculus) näo isogênicos foram infectados transcutaneamente com cerca de 450 cercárias (das cepas LE e SJ do S. mansoni) näo irradiadas (grupos controles) e irradiadas com 3 Krad de radiaçäo gama proveniente de cobalto-60, com a finalidade de observar o efeito da irradiaçäo gama sobre a fertilidade das fêmeas e a sobrevida dos vermes no sistema porta. A partir do 33§ dia ocorre uma certa estabilidade na populaçäo dos vermes sobreviventes, ficando esta populaçäo constante, notadamente em relaçäo à cepa LE, até o final das observaçöes (90§ dia). Concluiu-se que esta dose de radiaçäo gama impede a produçäo de ovos dos vermes em 98,1% dos camundongos infectados, sendo mortos todos os ovos detectados; as fêmeas säo mais resistentes à irradiaçäo e o efeito desta sobre a mortalidade dos machos somente se torna estatisticamente significativo a partir do 61§ dia de infecçäo. O longo tempo de permanência de vermes adultos irradiados estéreis no sistema porta de camundongos e o seu provável envolvimento no desenvolvimento de imunoproteçäo, tipo imunidade concomitante sem as implicaçöes imunopatológicas para o hospedeiro, säo discutidos nesse trabalho

[Schistosoma mansoni: quantitative aspects of the fertility and survival of worms of irradiated cercariae (3 Krad), in mice]. / Schistosoma mansoni: aspectos quantitativos da fertilidade e sobrevida de vermes oriundos de cercárias irradiadas com 3 Krad, em camundongos.

The effect of gamma irradiation on the fertility of female mice, as well as the survival of worms in their portal system, have been observed in four groups of outbred albino mice (Mus musculus), experimentally infected with ca 450 cercariae of Schistosoma mansoni (LE and SJ strains), by transcutaneous route. The cercariae used were a) non-irradiated (control groups), and b) irradiated with 3 Krad of gamma irradiation (Co-60). From the 33rd day on, some stability in the population of surviving worm could be observed. This population remained constant till the end of the observation period (90th day), notedly in relation to the LE strain. Thus, it was concluded that gamma irradiation (at the dose of 3 Krad) is able to hinder the worm egg production in 98.1% of the infected mice. Further, it was observed that the few detected eggs were dead. Females were found to be more resistant to irradiation. The irradiation effect on the mortality of male worms was statistically significant scarcely from the 61st day on. The long period of permanence of the sterile adult irradiated worms in the portal system of mice and their probable involvement in the development of immunoprotection (the so-called concomitant immunity, without the immunopathological involvements for the host) are here discussed.

An immunological analysis of natural resistance to mouse hepatitis virus (JHMV strain) infection in C3H mice.

1. Since the development of resistance against mouse hepatitis virus (JHMV strain) coincides with the maturation of the immune system, we studied the possible role of distinct immunological components in the resistance of adult mice during JHMV infection. 2. Adult C3H mice naturally resistant to JHMV were rendered susceptible to infection by lethal 60Co-irradiation and were subsequently reconstituted with limiting numbers of syngeneic bone marrow cells or spleen cells. 3. Resistance or susceptibility depended on the number of cells used for reconstitution and the interval between reconstitution and infection. Spleen cells from suckling mice affected neither resistance nor susceptibility and peritoneal cells from adult mice and thymus cells reduced resistance. Persistence of JHMV was demonstrated by virus reactivation. 4. Animals infected with JHMV only once before being rendered immunoincompetent showed a different pattern of resistance. One to four months after infection, 15 to 35% of the animals died after reconstitution without having been reinfected, and persisting JHMV was found in their liver, spleen and peritoneal exudate. The survivors (47 to 87%) were resistant to further JHMV infection during immunodeficiency. 5. Animals immunized 3 times with JHMV before irradiation did not show virus reactivation and were fully resistant to JHMV reinfection after reconstitution. The level of neutralizing anti-JHMV serum antibodies in the group of mice immunized only once was comparable with the level of those immunized 3 times. 6. The role of macrophage activation and cell-mediated immunity in this model are discussed as an explanation for the resistance to, and persistence of, JHMV.

Relación huesped-parásito en leishmaniasis / Host-parasite relation in leishmaniasis

Leishmaniasis es un conjunto de entidades clínicas que se manifestan como lesiones cutáneas, mucocutáneas o viscelares. Cada tipo tiene un comportamiento particular, aunque el agente causal es morfológicamente indistinguible. Se presentan aspectos observados en la relación huésped-parásito, esto es, la interacción entre Leishmania, macrófago y respuesta inmune del huésped