[The evaluation of cellular immunity in the aged by skin tests]

Cellular immunity of persons over 60 years of age was evaluated by intradermal testing with ubiquitous antigens, such as PPD, Trichophytin, Candidine and Varidase (SK, SD-40-10 U/ml) and by skin sensitization with DNCB. The group consisted of 290 individuals, 95 men and 195 women, without any signs of disease other than the usual geriatric disturbances, such as osteoporosis, ostearthritis and mild systolic hypertension. No medication was used that could interfere with the results of the tests. The patients were divided into 2 groups, group I, 190 cases between 60 and 75 years of age, and group II, 100 cases over 75.

Intradermal tests with all ubiquitous antigens were negative in 7,4% of group I and 13% of group II, while in a control of younger adults each had at least had 2 positive tests. This difference was mainly due to a lower sensitivity to PPD in the elder persons. 16% of group I and 23% of group II did not sensitize with DNCB. All skin tests, intradermal and DNCB, were negative in 1,1% of group I and 4% of group II. Our results suggest a decreasing immunological activity according age which could explain the higher incidence of infections, neoplasms and autoimmune diseases in old people. Also periodical repetition of the test in elderly people could evaluate immunological competence and, consequently, susceptibility to these diseases. Patients with negative tests or only one positive test, should be carefully investigated in order to exclude the existence of pathology. Our results and considerations also suggest the possibility that, by increasing immunological reactivity, the occurrence of certain diseases could the prevented.