Skin test reactivity to H. influenzae antigens as an outcome of the antigen structure and the balance between humoral and cell-mediated immunity in rats.

Wistar RA rats were skin tested with several antigens prepared from Haemophilus influenzae, including a soluble (RE) and suspended form (CRE) of a somatic H. influenzae antigen, a preparation of bacterial capsular antigens (CA) and inactivated H. influenzae bacteria. The animals skin tested were passively sensitized with antigen-specific lymphoid cells or with antigen-specific antisera. Some animals were sensitized with a combination of specifically sensitized lymphoid cells and a specific antiserum. Delayed hypersensitivity skin reactions were only observed after a cell transfer and using suspended antigen forms (CRE and inactivated H. influenzae). Using the soluble antigen form a delayed decreased reactivity was found after an identical cell transfer. On the other hand Arthus reactivity of the skin was only observed after a transfer of an antigen specific antiserum and using soluble antigen forms (RE and CA). The suspended form showed when used under these circumstances an opposite effect: a decrease of the normal inflammatory reactivity was found. These results were interpreted as a support to the idea that the sensitization procedure (humoral vs cellular) is of importance to the character of the allergic reaction (immediate vs delayed); while the nature of the antigen seems to influence the intensity of the reaction (increase or decrease of the normal inflammatory response). Furthermore it was shown that antigen-specific antibodies were able to block the development of a d.h.-reaction to H. influenzae; while on the other hand specifically sensitized cells interfered with the development of an Arthus reaction to somatic H. influenzae antigen. The usefulness of the described H. influenzae antigens as skin test antigens is probably dependent on the blocking effects of either humoral cellular immune systems and is discussed.