Diversity in the T cell response to Chlamydia-sum are better than one

Chlamydia trachomatis is responsible for an increasing number of sexually transmitted infections in the United States and is a common cause of serious pathology in the female reproductive tract (FRT). Given the impact and incidence of these infections, the production of an effective Chlamydia vaccine is a public health priority. Mouse models of Chlamydia infection have been utilized to develop a detailed and mechanistic understanding of protective immunity in the FRT. These studies reveal that MHC class-II restricted Chlamydia-specific CD4 T cells are critical for primary bacterial clearance and provide effective protection against secondary infection in the FRT. Despite the clear importance of IFN- γ produced by CD4 Th1 cells, there are also suggestions of wider functional heterogeneity in the CD4 T cell response to Chlamydia infection. Understanding the role of this diversity in the CD4 T helper cell response in the FRT should allow a more nuanced view of CD4 T cell biology in the context of Chlamydia infection and may be critical for vaccine development. Here, we summarize our current understanding of CD4 T helper subsets in the clearance of Chlamydia and discuss some areas where knowledge needs to be further extended by additional experimentation.