Cells with CD4 receptor on surface T lymphocytes (T helper) T-cell precursors in the bone marrow and thymus Monocytes/macrophages Dendritic cells (in the lymphatic organs, gut, genitourinary tract, submucosal tissue) Microglia cells (in the central nervous system) Retinal cells Co-receptors: CCR5, CXCR4

Pathogenesis HIV enters the susceptible cells, replicates and spreads in the body of the host. Cell - mediated immunity is activated and kills the virus particles. Specific antibodies are produces to fight the infection (humoral immunity). Some viruses reach the reservoirs ( eg.lymph nodes, brain, urogenitary tract) and are safe from antibodies and killer cells. The rate of replication gets established (set point). HIV destroys T-lymphocytes (lysis, apoptosis), new lymphocytes are being produced (balance). T-lymphocytes count declines (immunodeficiency)

Surface pathogens Skin Streptococci, staphylococci Mucose membranes Streptococci, staphylococci, candida sp., anaerobic bacteria (fusobacterium) Pulmonary alveoli – cryptococci, Pneumocystis carinii GI tract – Escherichia coli Saprofites are useful in immunocompetent patient.

Latent infections Early colonization of the body Pathogen Site of survival HSV VZV EBV CMV Toxoplasma gondii Dorsal root ganglia ” ” ” Mucous membrane of the mouth and throat – B lymphocytes Macrophages Tissue cysts in various organs

Sequelae of lymphocytes CD4 deficiency Activation of surface pathogens Candida albicans Cryptococcus neoformans Pneumocystis carinii Reactivation of latent infections Herpes simplex virus (HSV) Varicella-zoster virus (VZV) - shingles Cytomegalovirus (CMV) Toxoplasma Epstein – Barr virus (EBV) Developing of neoplasms Kaposi`s sarcoma Non-Hodgkin`s lymphoma Cervical carcinoma Insufficient serologic response to new antigens New infection – serologic diagnostic tests unreliable, Vaccination – poor response (if any)

HIV / AIDS HIV infection ↓ Depletion of CD4 lymphocytes Immunodeficiency Opportunistic infections (reactivation) Specific tumors