CD4 and infection: where the 1st term describes the constant influx of CD4+T cells from the thymus, the 2nd term describes antigen-induced division, the 3rd term describes the loss due toinfection by wt viruses and population of wt virus-infectedmacrophages, the 4th term describes the infection by mutatedviruses and population of mutant virus-infected macrophages,the 5th term describes the homeostatic proliferation, and the6th term describes natural cell death.