Background: Increased hypersensitivity reactions to Propionibacterium acnes may be involved in the pathogenesis of severe acne.
Objective: To study delayed and immediate hypersensitivity reactions to P. acnes in patients with severe nodular acne (SNA) and acne fulminans (AF).
Methods: We performed lymphocyte stimulation and skin tests for P. acnes antigens on 11 patients with SNA and 7 patients with AF.
Results: The patients with SNA had similar mean lymphocyte stimulation indices (mean 13.96, SD 8.6) to P. acnes during active disease as had healthy controls (12.63, SD 6.46). After the treatment the mean stimulation index was significantly elevated (23.47, SD 13.84, p = 0.006). A similar increase occurred in the patients with AF (mean 17.04, SD 5.74, and 33.42, SD 27.17, respectively). Two of 7 patients with SNA and 3 of the 7 patients with AF but none of the 10 control subjects showed positive 48-hour intradermal tests to P. acnes.
Conclusion: Specific cell-mediated immunity to P. acnes increases during the course of severe inflammatory acne.