The previously suggested mathematical models of CD4+ lymphocyte depletion in HIV-infected individuals are analysed from the point of view of fundamental cell interaction mechanisms involved. Under the assumption of growth restriction of the HIV by cytotoxic lymphocytes, the intensity of the feedback mechanism increasing the influx of immature CD4+ lymphocytes and the intensity of the helper effect of CD4+ lymphocytes during the maturation of cytotoxic cells are evaluated and compared in a wide range of the respective model parameters. In this respect also the role of the proliferation rate of these cytotoxic lymphocytes under antigenic stimulation by HIV products is discussed. In addition, an alternative elimination mechanism of CD4+ lymphocytes is investigated, which assumes their destruction by cytotoxic lymphocytes. It is concluded that any of the considered cases of the influx amplification parameter, helper effect intensity parameter, and CD4+ lymphocyte elimination mechanism can be used for a qualitative adjustment of the model to clinical data.