Survival of pathogenic organisms in immunocompetent hosts.

Pathogens have evolved highly individual means of immune evasion. These involve their location within relatively shielded sites, the variability shedding or disguise of surface antigens and modifications of the host immune response. The latter include the use of proteases to split surface-bound antibodies, the production of compounds which consume complement, the avoidance of phagocytosis or the evasion of lysosomal systems of phagocytes and the excretion of products which inactivate effector functions of specific host cell populations. The continued study of immune evasion will enhance understanding of parasitism and promote the means for controlling organisms which are important pathogens of man and domestic animals.