Final answer:
Naive T cells, which do not recognize bacterial antigens presented by dendritic cells, contain receptors that stay in contact with other immune cells until they encounter their specific epitope. These cells express CD4 or CD8 coreceptors determining their interaction with MHC class I or II molecules on APCs. Upon activation by the epitope, they contribute to the immune response and create memory T cells for faster future responses.
Step-by-step explanation:
Understanding Naive T Cells and Antigen Recognition
Receptors on most naive T cells will not recognize bacterial antigens displayed by dendritic cells, and as a result, these T cells continue their circulation, maintaining contact with the population of T and B cells. These naive T cells are essentially on 'standby', waiting to encounter their specific antigenic determinant, or epitope, presented by antigen-presenting cells (APCs) like dendritic cells, to become activated. Naive T cells express one of two surface molecules, either CD4 or CD8, which are important in determining the interaction with MHC class I or MHC class II molecules on APCs, respectively, and are thus considered coreceptors.
When naive CD4+ T cells encounter an antigen-presenting dendritic cell with MHC II molecules displaying an epitope, they become helper T cells (TH). Similarly, CD8+ T cells are activated when they encounter MHC I molecules on APCs, leading to their development into cytotoxic T lymphocytes (CTLs). Without APCs presenting antigens, these naive T cells remain unactivated within the immune system.
The dendritic cells, with roles also played by B cells and macrophages, display processed antigens to activate the suitable T cells. Once activated, T cells migrate through the lymphatic system and circulatory system to the site of infection, contributing to the immune response against the pathogen. Should a subsequent encounter with the same pathogen occur, long-lived memory T cells are prepared to initiate a faster and more targeted immune response.