RESUMO
Malnutrition, infectious and toxic stress, hormonal and enzymatic deficiencies as well as graft versus host reactions during the last trimester of pregnancy and during the first six months of life lead to persistent depressions of cell mediated immunity. The subsequent imbalance between the cell mediated and humoral system of immunity leads to differences in disease prevalence in poor and rich populations. Particularly leprosy, tuberculosis, viral disease as for instance frequently fatal measles and diseases due to complexes between humoral antibody and bacterial components as for example acute rheumatic fever occur with increased frequency in B (+) T (-) populations. Desturbances of immune surveillance due to suppression of specific cell mediated immune function leads to an increased frequency of neoplasia, particularly B-cell lymphoma and gastrointestinal tumors. Populations in which the T-cell system can mature without interference show a trend towards diseases in which excessive T-cell response plays a major role, as for instance rheumatoid arthritis, Sjögren syndrome, terminal ileitis, autoimmune angiopathies, multiple sclerosis and possibly also disseminated lupus erythematodes.