Immune Response

to Intracellular Pathogens

Hera Nirwatihnirwati@yahoo.comDept. of Microbiology

Fac. of Medicine Universitas Gadjah Mada

Outline

• Two types of immune response to intracellular pathogens:

• Innate Response:

• Phagocytic cells

• IFN

• NK cells

• Adaptive Response:

• T cells

• B cells

Pathogens can be found in various compartments of the body, where they must be combated by different host defense mechanism

Immune Response to Pathogens

Innate Response to Intracellular pathogens

Infections and the responses to them can be divided into a series of stages

Mechanism of phagocytosis

Important cytokines and chemokines secreted by dendritic cells and macrophages in response to bacterial products include IL-1β, IL-6, CXCL8, IL-12 and TNFα

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Interferons are antiviral proteins produced by cells in response to viral infection

Killing by NK cells depends on the balance between activating and inhibitory signals

Adaptive Response to Intracellular

pathogens

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MHC class I molecules present antigen derived from proteins in the cytosol

CD8 cytotoxic T cells are specialized to kill cells infected with intracellular pathogens

Cytotoxic T cells kill target cells bearing specific antigen while sparing neighboring uninfected cells

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The humoral immune response is initiated when B cells that bind antigen are signaled by helper T cells

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The immune response to intracellular bacteria is coordinated by activated Th1 cells

Mycobacterium tuberculosis

The inner layer is composted of peptidoglycan which is covalently linked to arabinogalactan layer. The outer membrane contains mycolic acids, glycolipids

like (mannose-capped) lipomannan, and mannoglyco- proteins.

PIM: phosphatidyinositol mannosides

Figure 11-15

Granulomas from when an intracellular pathogen or its constituents cannot be eliminated completely

Immune response to M.tuberculosis

Human Immunodeficiency Virus (HIV)

Figure 11-23

Figure 11-25

Immune response to HIV

Figure 11-20

Figure 11-29

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Innate & Adaptive Immune Responses Against Viruses

Immunity against viruses functions to prevent infection and to eradicate established infection. Innate immunity is mediated by type I IFNs, which prevent infection, and NK cells, which eliminate infected cells. Adaptive

immunity is mediated by anti bodies and CTLs, which also block infection and kill infected cells, respectively.

The innate immune response to intracellular bacteria consists of phagocytes and NK cells,interactions among which are mediated by cytokines (IL-12 and IFN-γ). The typical adaptive immune response to these microbes is cell-mediated immunity, in which T cells activate phagocytes to eliminate the microbes.

Innate and adaptive immunity to intracellular bacteria.

Thank You