Cellular Immune Response of Adenoidal and Tonsillar Lymphocytes to the P6 Outer Membrane Protein of Non-typeable Haemophilus Influenzae and its Relation to Otitis Media

Abstract

Cellular immune responses to the P6 outer membrane protein of non-typeable Haemophilus influenzae (NTHi) were determined in vitro by measuring immunoglobulin (Ig) secreting cells and lymphocyte proliferation in adenoidal and tonsillar lymphocytes from 19 children. Preliminary tests showed that P6 did not stimulate naïve cells such as cord blood lymphocytes, but did stimulate sensitized cells in adenoids and tonsils. Cellular proliferation was significantly higher in adenoidal lymphocytes than in tonsillar lymphocytes (median: quadratile of stimulation index=3.7:2.3-5.5 vs. 1.2:1.0-2.1, p<0.02). A comparison between children with or without otitis media revealed that proliferative responses to P6 of adenoidal lymphocytes from children with otitis media were significantly decreased (2.0:1.8-3.6 vs. 3.7:2.3-5.5, p<0.04). P6-specific antibody secreting cells were identified in a total of 14 adenoids and the number of cells secreting IgA was decreased in the otitis media group compared to controls (median: quadratile/10⁶ cells=435:359-499 vs. 755:593-1870, p<0.05). Cultivation with P6 stimulated IgA secretion in children without otitis media, while no response was seen in children with otitis media (median: quadratile/10⁶ cells=1323:915-2410 vs. 2240:1900-2830, p<0.02). These preliminary data demonstrate that lymphocytes from adenoids and tonsils recognize P6 as a specific antigen and that the adenoid is the more reactive of the two organs. Impaired P6-specific cellular immune responses of adenoids in children with otitis media may explain the recurrent nature of otitis media due to NTHi in the otitis prone population.