This series of graphics have been designed to explain the dissemination of HIV from site of infection to secondary lymphoid tissue.
HIV dissemination to secondary lymphoid tissue
Dissemination of HIV from the site of infection to secondary lymphoid tissue can be due to migration of activated macrophages infected with HIV or migration of activated dendritic cells carrying surface-bound infectious virions to the T cell zone of secondary lymphoid tissue. Once the cells reach this zone antigen is presented to T cells. In this way, CD4+ helper T cells, which are the preferred targets of HIV, become infected by contact with virus and in turn can spread virus to other tissues following activation and migration out of lymphoid organs. Follicular dendritic cells in germinal centres also trap infectious virus on the cell surface and can infect T cells entering the lymph node via afferent lymphatics or T cells associating with B cells in germinal centres. Activated CD8+ cytotoxic T cells expand in the lymph node to kill the virus-infected cells.
Lymph node damage
Over time, the structure of secondary lymphoid tissue becomes damaged by HIV infection and contributes to CD4+ helper cell loss and failure to mount effective immune responses against opportunistic infections. Fibrosis (collagen deposition) in the lymph node limits total volume and obstructs T cell entry and motility.