Host defense mechanisms resistance

Infections Corticosteroids may mask signs of infection, and new infections may appear during their use. There may be decreased resistance and inability of the host defense mechanisms to prevent dissemination of the infection. Restrict use in active tuberculosis to cases of fulminating or disseminated disease in which the corticosteroid is used for disease management with appropriate chemotherapy. Corticosteroids may exacerbate systemic fungal infections and may activate latent amebiasis. 

In some cases, xenobiotic compounds adversely alter host defense mechanisms. This may reduce the body s ability to resist pathogenic bacteria or viruses or to combat neoplasia (tumor tissue). 

In vivo, interferon inducers exert a wide variety of effects on host defense mechanisms interferon production, pyrogenicity, stimulation of cellular and humoral immunity and stimulation of reticulo-endothelial activity. It is not surprising, therefore, that interferon inducers increase the host s resistance to both viral and non-viral (bacterial, fungal, protozoal) infections and tumor growth. A major obstacle confronting the clinical usefulness of interferon inducers is their toxicity. Are interferon induction and toxicity necessarily coupled or can they be disconnected Preliminary evidence suggests that, at least with poly(I) poly(C), toxicity and activity could be uncoupled. 

Plants are continually exposed to a vast array of potential phytopathogenic fungi nevertheless, plants resist to most of them by blocking fungal development soon after penetration. Resistance against pathogens can be distinguished in resistance at the species level (non-host resistance) and resistance at the cultivar level (race-cultivar resistance). Plants lack a circulatory system and antibodies and have evolved a defense mechanism that is distinct from the vertebrate immune... 

In addition to its role as a preformed resistance factor, Hijwegen (5) has also proposed active induction of lignification as a defense mechanism of cucumber against Cladosporium. Subsequently, in a number of host-pathogen interactions, induced lignification has been proposed as the active... 

Three basic approaches are used to control viral diseases vaccination, antiviral chemotherapy, and stimulation of host resistance mechanisms. Vaccination has been used successfully to prevent measles, rubella, mumps, poliomyelitis, yellow fever, smallpox, chickenpox, and hepatitis B. Unfortunately, the usefulness of vaccines appears to be limited when many stereotypes are involved (e.g., rhinoviruses, HIV). Furthermore, vaccines have little or no use once the infection has been established because they cannot prevent the spread of active infections within the host. Passive immunization with human immune globulin, equine antiserum, or antiserum from vaccinated humans can be used to assist the body s own defense mechanisms. Intramuscular preparations of immune globulin may be used to prevent infection following viral exposure and as replacement therapy in individuals with antibody deficiencies. Peak plasma concentrations of intramuscular immune globulins occur in about 2 days. In contrast, intravenously administered immune globulin provides immediate passive immunity. 

Levitz SM Overview of host defense in fungal infections. Clin Infect Dis 1992 14 37-42. Romani L, Howard DH Mechanisms of resistance to fungal infections. Curr Opin Immunol 1995 7 517-523. 

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