Mab 502 recognizes the 60 kD outer membrane complex protein present in the periphery of reticulate bodies (RBs) and identifies all serotypes (serovars A-C, D-K and L1-L3) of C. trachomatis as well as Chlamydophila psittaci and Chlamydophila pneumoniae. The epitope is also present on elementary bodies (EBs) of C. trachomatis C-complex serotypes.