T ganism are believed to be influenced by specific gene action and by response to all kinds of antigens16 The specific genes supply the necessary genetic information for synthesis of the many antibodies, specific, nonspecific,14 or for response by production of immunologically competent cells to encounter different forms of antigens or their combination with basically non-antigenic s~bstances.~5 The total nonspecific immunity and the presence of immunologically competent cells cannot be measured accurately by present methods, but some of its forms, namely, the delayed hypersensitivity response (DHR) can be investigated. The purpose of the present study was to inquire how far DHR is influenced by aging, exposure to chronic bacterial diseases and cancer. In the past, the evaluation of immunological competence in patients with neoplasm was measured by the level of circulating antibodies and very few studies were conducted to evaluate the level of cellular antibodies or immunologically competent cells. The experimental production of DHR by intracutaneous injections24 usually is accompanied by simultaneous development of circulating antibodies; however, if the DHR is elicited by the topical application of certain simple chemicals, no circulating antibodies deve10p.~ Simple chemicals like dinitrochlorbenzene are bound to amino acids or possibly .~