ABSTRACT
This chapter suggests that the most likely form of antigenic variation for Chlamydia trachomatis is allelic variation. Antigenic variation of the chlamydial major outer membrane protein may play a role for T-cell determinants. T-cells recognize peptides that differ from the antigens recognized by antibodies. The development of serovar-specific monoclonal antibodies to C. trachomatis confirmed the presence of surface-exposed serovariant epitopes. The application of monoclonal antibodies for typing chlamydial isolates has also revealed additional serovars that are not discriminated using polyvalent sera. There are two reasons why the role of antigenic variation in chlamydial pathogenesis appears unclear. One is that this is not the only strategy of immune evasion in the chlamydial repertoire, and the second is related to mucosal niche of the organisms. Within the spectrum of antigenic variation, C. trachomatis has limited capacity since a given genotype cannot switch the expression of antigenic types.
