o:30748 Report on lower anti-pneumococcus IgG1 levels in men, especially over the age of fifty en Streptococcus pneumoniae, the pneumococcus is an important human pathogen. It possesses a capsule which has been thoroughly studied, since it is an important factor in virulence. In this work S. pneumoniae ATCC 6301, belonging to Serogroup 1, was used as a model organism to determine the levels of different IgG isotypes specific to this bacterium in different sex and age groups. For this purpose an in‐house ELISA was used. Although IgG2 is a major antibacterial antibody subclass, acting against polysaccharide antigens, the level of pneumococcus‐specific IgG2 did not differ from the level of IgG2 specific to several tested lactic acid bacteria (LAB). On the other hand pneumococcus specific IgG1 level was significantly higher to the level of LAB specific IgG1. This is most likely a consequence of previous encounters with pathogenic pneumococcal microorganism and a distinguishing characteristic of this encounter. By analyzing different sex and age groups we found significantly lower anti‐pneumococcus IgG1 levels in men, implying lower protection against invasion with pneumococcus, which possibly translates to other encapsulated bacteria. The Covid‐19 pandemic has identified males as being at increased risk of hospital admission and death and lower levels of anti‐pneumococcus antibodies might be a contributing factor. Hence, we advocate the immunization with conjugate pneumococcal vaccines in male individuals, especially over the age of 50. Adaptive immunity, ageing, antibody 1552101 0014-2980 1552099 10.1002/eji.202170200 2023-09-07T11:51:20.649Z 44 yes 46 Sanja Knežević Institute of Virology, Vaccines and Sera, Torlak, Belgrade, Serbia Dejana Kosanović Institute of Virology, Vaccines and Sera, Torlak, Belgrade, Serbia person Irena Živković Institute of Virology, Vaccines and Sera, Torlak, Belgrade, Serbia person Vesna Ilić Institute for Medical Research, Belgrade, Serbia person Luka Dragačević Institute of Virology, Vaccines and Sera, Torlak, Belgrade, Serbia person Ljiljana Hajduković University of Belgrade, Institute for the Application of Nuclear Energy INEP, Serbia doktor biohemijskih nauka person 0000-0003-0720-2345 Rajna Minić Institute of Virology, Vaccines and Sera, Torlak, Belgrade, Serbia person application/pdf 12246347 https://phaidrabg.bg.ac.rs/o:30748 no yes 1 70 92000004 11A29 11A2903 11A25 European Journal of Immunology, Supplement S1, Virtual ECI 2021, Abstract Book 51 Supplement S1 337 Wiley 2021