Fig. 14: Activation of a Macrophage by a Th1 Lymphocyte

1. Engulfed bacteria inside a phagosome or a phagolysosome.
2. An activated TH1 lymphocyte binds to a peptide/MHC-II complex on a macrophage by way of its TCR and CD4 molecule. Co-stimulatory molecules such as CD40L on the TH1 cell then bind to CD40 on a macrophage.
3. This triggers the TH1 lymphocyte to secrete the cytokine interferon-gamma (IFN-γ) that binds to IFN-γ receptors receptors on the macrophage.
4. The IFN-γ activates the macrophage enabling it to produce more hydrolytic lysosomal enzymes, nitric oxide, and toxic oxygen radicals that destroy the microorganisms within the phagosomes and phagolysosomes.

Doc Kaiser's Microbiology Home Page
Copyright © Gary E. Kaiser
All Rights Reserved
Jan., 2008

Please send comments and inquiries to Dr. Gary Kaiser