JournaloflmmunologicalMethods, 83 (1985) 353 361 353 Elsevier JIM03654 The Use of Somatic Antigen of Haemophilus influenzae for the Monitoring of T Cell-Mediated Skin Test Reactivity in Man Ella M. Van de Plassche-Boers *, Hemmo A. Drexhage and Marjan Kokj6-Kleingeid Department of Pathology, LaboratotT for Clinical lmrnunologv, Free Unit,erm O" ltospital. Amsterdam. The Netherland~ (Received 10 April 1985, accepted 2 July 1985) To investigate its usefulness as a skin test antigen, Haemophilus influenzae somatic antigen was tested in 28 healthy individuals, both in soluble and aggregated form. All subjects were found to possess specific antibodies against H. influenzae of both IgG and IgM subclass, thus showing their previous exposure to this commensal micro-organism. The somatic antigen in solution was found to be a poor antigen for eliciting a delayed hypersensitivity skin response: only 2 out of 16 subjects reacted with a positive DTH pattern. In contrast, 25 out of 28 persons showed a positive DTH pattern when somatic antigen was used in aggregated form. Two types of DTH reaction patterns could be detected (in a ratio of approximately 3 : 2), viz. those with an early (24 h) and those with a late (48 h) maximal swelling. Histology of 3 early and 1 late DTH reaction showed perivascular infiltrates of mainly Th~tp~r/T,,do,.¢,. lymphocytes, ttardly any basophils were seen. One negative skin test, biopsied at 6 h, showed no signs of Arthus reactivity. It can be concluded that skin tests using the aggregated form of the somatic antigen of H. infhwnzae are useful for assaying specific T-cell-mediated reactivity in man. Key words: skin test - DTH reactwi O' - Haemophilus influenzae Introduction In a number of clinical conditions, such as immunodeficiencies, cancer and autoimmunity, it is of value to measure the function of the T cell system (Spider, 1980). Delayed-type hypersensitivity (DTH) skin tests employing antigens derived from micro-organisms such as M. tuberculosis (e.g. PPD), streptococci (e.g. SK-SD) and Candida albicans are used for this purpose (Spitler, 1980). Unencapsulated Haemophilus influenzae also contains T cell-mediated immunity- inducing somatic antigens (Hoeksma, 1972). In this paper we report the usefulness of * Correspondence to: E.M. Van de Plassche-Boers, Laboratory for Clinical Immunology, Department of Pathology, Free University Hospital, De Boelelaan 1117, 1007 MB Amsterdam, The Netherlands. 0022-1759/85/$03.30 :,~:'1985 Elsevier Science Publishers B.V. (Biomedical Division)