Figure 1-20To summarize/recapitulate the whole process: 1. Dendritic cell scavenges particles and carries them to the lymph node whereit presents oligopeptide fragments via its MHC Class II to helper T cells2. If a helper T cell recognizes the presented oligopeptide antigen, it becomesactivated and looks around for a B cell that may also display the sameoligopeptide antigen (via MHC class II) on its surface.3. If it finds such a B cell, it causes the B cell to become activated, causing theB cell to mature into a plasma cell and to release large amount of solubleantibody molecules -- the humoral immune response!1.2.3.THTHdendritic cellresting macrophageactivated macrophageantibodiesAttack & engulf infectious agents &kill antibody-coated cellsAnother type ofCELLULAR RESPONSETHTHdendritic cellresting macrophageactivated macrophageantibodiesAttack & engulf infectious agents &kill antibody-coated cellsNote the dual role of helper T (TH) cellsin facilitating both humoral and cellular immune responses THFigure 11-30The manifestations of AIDSindicate defects in multiple arms ofthe immune system.HIV incidence worldwideFigure 11-19AIDS in hemophiliacs receiving HIV-contaminated bloodFigure 11-20CD4+ T cells =Helper T cells = TH cells Figure 11-21A retrovirus that resembles RSV except that it’s much more complicatedA retrovirus that resembles HIV except that it’s much more complicatedNote that the integrated provirus may eitherbe transcribed or be repressed.host cellchromosomeNote that if the proviral transcriptionis repressed, the immune system hasno way of knowing that a cell harborsa latent HIV infection.progeny virionsHIV originated in monkeys andWas carried via inter-species Transmission into humans50-70 years ago somewhere in Central Africa. Figure 11-22CD4+ T cells =Helper T cells = TH cells HIV adsorbs to the surface of host cells by attaching to host cell receptors. The CD4 protein is used by TH cellsto recognize and bind the MHC Class II proteins usedby the professional antigen-presenting cells -- the dendritic cells, macrophages and B cells.Figure 11-23 part 1 of 2Figure 11-23 part 2 of 2cytoplasmnucleusplasma membraneFigure 11-23Figure 11-24 (viral glycoprotein) env gagThe HIV l RNA encodes many viral proteinsAmong other functions,The virus can controlWhich of its mRNAs isExported from the nucleusTo the cytoplasmFigure 11-25 provirus NF-!B = host-cell transcription factornucleuscytoplasmplasma membraneprogeny virusparticlesFigure 11-25 part 1 of 3Note that the state of Physiologic activation of the hostT-cell determines whether or notNF-kB is made and therefore whetherthe provirus is transcribed.Figure 11-25 part 2 of 3Progeny virus particles budding from HIV-infected cellFigure 11-29CTL = cytotoxic T cells - TC (attack HIV-infected cells)log scalep24 = gag-nucleoprotein coreNote cyclic appearance anddisappearance of viral titersTH cells - helper T cells Eventually the continued cycles of infection into helper T cells results in their depletion and the resulting increasein viral titer in the serum as the immune system loses itsability to suppress viral replication.Immune evasion through periodic changes in the HIVenvelope glycoproteinNote that the only viral protein thatprotrudes from the virion is the envelopeglycoproteinPeriodic changesin the structure ofthe viral glycoproteinallow the virus toescape neutralization byexisting antibodies, forcing the immunesystem to develop newones. Drugs can be developed to antagonize the viral reverse transcriptase(as well as other virus-encoded proteins, not shown here). The viral reverse transcriptase enzymeFigure 11-26Effects of combination anti-HIV drug therapy on the no. of viralRNA molecules in the plasma of a virus-infected individual(One of these drugs may shut down the viral reverse transcriptase, while another may shut down the viral protease needed for the post-translationalprocessing of the viral Gag polyprotein, cleaving it into nucleocapsid proteins.)Figure 11-28Effects of the use of combination drug therapy on thedeath rate and infectious complication rate of
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