phagocytosis Flashcards
pathogen toolbox to keep phagocytosis in check (3)
- kill phagocytes
- block or avoid phagocyte attack
- grow in phagocytes
mycobacterium tb avoids phagocytosis by
growing in phagocytes
phagocytosis function of eosinophils is involved with with virus
malaria
Long lived Present in tissues (when mature) O2-dependent killing not vigorous Conditions amenable for intracellular growth of pathogens Pathogen tactics in battle: Circumvent respiratory burst Break out of phagosome Prevent phagolysosome fusion Resist granule contents
macrophages
Short lived Circulating Respond to conditions stimulating Inflammation, leaving circulation Vigorous respiratory burst during phagocytosis Extremely hostile environment for intracellular pathogens. Pathogen tactics: a. Resist phagocytes b. Kill or be killed
polymorphs
dendritic cells have more MHC I or II
II
2 opsonization proteins
- c3bi
2. IgG
phagocytic receptors such as integrins/complement receptors, lectins and Fc-receptors are involved in what mechanism of phagocytosis
opsonization
classical pathway of the complement system
antigen ab complexes
MB-lectin pathway of the complement system
lectin binding to pathogen surfaces
*** direct recognition of specific carbohydrates a specific receptor
alternate pathway of the complement pathway
pathogen surfaces
** allows pathogens to be recognized in absence of ab
dectins: the major class of phagocyte lectins is involved in recognition of _____ pathogens
fungal
these receptors are involved in:
- toll like receptors
- Il-2 receptor
- TNF receptor
- iFN gamma receptors
macrophage
activation is through inflammation and bacterial/viral disease
macrophages release what type of cytokines?
what does it leads to?
secretion of IL-2 allows the differentiation of CD4 helper T cells
toll-like receptor ligand:
Lipoproteins and yeast CHO fragments
TLR2- found in mammalian cells to recognize micro-organisms
selectins and integrins are important in the response to infection by
adhesion and transmigration receptors
antimicrobial activity begins before the microbe is completely engulfed
yeppp
missing leukocyte
integrins. Usually lethal.
Leukocyte Adhesion Deficiency:
missing NADPH
oxidase components. Capsulated bacteria cause
serious disease
Chronic Granulomatis Disease:
delayed phagosome-
lysosome fusion and low chemotaxis. Recurrent
infections.
Chediak-Higashi Syndrome:
no peroxide dependent
halogenation of microbes. Patients healthy.
Myeloperoxidase Deficiency:
in response to microbial adhesion NADPH Oxidase releases
O2-
in the 2nd killing mechanism there is suicide by NADPH oxidase that releases
antimicrobial “NETS”
*** works particularly well for gram positive organism such as strep
killing mechanims 3 involves
antimicrobial peptides such as defensins/cathelicidin by directly attaching to the gram positive membranes and putting holes in the membranes
if all else fails in killing what happens
nitric oxide killing by macrophages s
Inhibit opsonization or inactivate phagocytosis
1. S. pneumoniae 2. S. pyogenes 3. RhoGAP proteins
- Capsule: S. pneumoniae
- M protein: S. pyogenes
- Disrupt signaling: RhoGAP proteins
