Bacterial Resistance and Toxins Flashcards
What is the best known of the nutritional defenses associated with?
the derivation of iron from host tissues
How do pathogenic bacteria derive iron from the host?
- producing iron chelating compounds that scavenge iron by competing directly with transferrin and lactoferrin of the host 2. directly removing iron from iron-binding proteins via receptors on the bacterial surface 3. bacteria can obtain iron through degradation of iron-binding and heme-containing proteins
What are the specific bacterial resistance mechanisms?
toxins, avoidance of phagocytosis, inconspicours adherence, parasitism of nonprofessional phagocytes. walling off
How do bacteria survive and grow inside phagocytes?
disrupt phagosome or phagolysosome
prevent phagosome-lysosome fusion
abrogate the oxidative burst
destroy oxygen radicals
modify effects of antibacterial peptides in the phagolysosome
What is the role of toxins in bacteria?
interfere with cell membrane function
interfere with chemotaxis
leukotoxins or cytotoxins that have direct toxic effects on specific cell types (….?)
How do capsular polysaccharides avoid phagocytosis?
they cement organisms together to prevent opsonization by antibody, complement, or other serum proteins and they make organisms less hydrophobic
The mycoplasmas lack a ____ ______ and have a cell membrane that essentially mimics the _____ _______ of the _______.
cell wall, plasma membrane, phagocyte
How do bacteria avoid professional phagocytes?
some bacteria enter cells other than phagocytes (intestinal epithelial cells, bone marrow, etc.) and are thereby shielded from the professional phagocytes
How do abscesses become walled off?
some bacteria stimulate the host to form a wall around them so that they are not exposed
How can bacteria circumvent the cellular immune response?
- changing the antigens on their surfaces or 2. suppression of the immune response (chronically infected macrophages may produce prostaglandin E2 and other factors that suppress lymphocyte proliferation)
Are T-cells required for simple polysaccharides to stimulate an immune response?
no
For a t-independent immune response, what is the ontogeny of the response?
late
Is there induction of memory in the T-independent response?
no
Is there isotype restriction in the T-independent response?
yes
Is there affinity maturation in the T-independent response?
no
For complex polysaccharide and protein antigens, are T cells needed for an immune response?
yes
What is the ontogeny of response for T-dependent response?
early
Is there induction of memory in the T-dependent response?
yes
Is there isotype restriction for the T-dependent response?
no
Is there affinity maturation in the T-dependent response?
yes
How can simple polysaccharides be converted to T-cell dependent antigens?
by complexing them with protein or some other more antigenically complex material that increases the immunogenicity of the bacterial polysaccharide
What are the steps of the exogenous pathway?
- organism or protein is phagocytosed or endocytosed 2. organism or protein is broken down into antigenic peptides in the phagosome 3. antigenic peptides associate with MHC Class II molecules 4. antigenic peptides are presented to CD4+ T-cells 5. CD4+ T-cells produce cytokines. The end results are either a cytotoxic response or the stimulation of B-cells to produce antibody
What are the steps of the endogenous pathway?
- organism replicates in the cytoplasm of the host cell 2. organism is degraded into antigenic peptides by cytoplasmic enzymes 3. antigenic peptides associate with MHC Class I molecules 4. antigenic peptides are presented to CD8+ T-cells 5. CD8+ T-cells kill host cells that are infected with viruses, bacteria, or parasites
Where does the toxic effect reside in bacterial toxins?
lipid A
How does endotoxin act on cells?
it binds to CD14 with the help of lipopolysaccharide binding protein (LBP)
Draw an endotoxin.
Should look like this
