Q. What are CD4 lymphocytes? What is the relationship between these cells and HIV? How does HIV replicate?

The CD4 lymphocytes are T helper lymphocytes that present in their plasma membrane receptor proteins called CD4.

The CD4 lymphocytes are the cells that HIV infects and within which the virus replicates. The HIV has proteins in its capsule that bind to the CD4 receptors of lymphocytes. By that bond the virus fuses with the cell membrane and its content (RNA, reverse transcriptase, protease, and so on.) penetrates into the cytoplasm and the viral replication process begins.

The HIV RNA is then converted into DNA by the reverse transcriptase. The new DNA is put-in into the genetic material of the lymphocyte with the aid of enzymes called as integrases. By translation and transcription this DNA commands the synthesis of proteins necessary for the assemblage of new viruses. The Long polypeptides are thus produced and then fragmented into proteins and viral enzymes by the enzyme protease so new HIV viruses are assembled and break the cell membrane to gain the circulation.