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Explain innate immunity.
What types of cells would mediate innate immunity? (p.1)
- Present at birth
- Activates in same manner every time
- Not antigen specific
- Primarily mediated by cells involved in inflammatory process:
- - polymorphonuclear leukocytes - basophils, neutrophils, eosinophils
- - macrophages
- - platelets
- Also involves complement cascade
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Explain adaptive immunity.
What types of cells would mediate adaptive immunity? (p.1)
- Acquired after birth
- Occurs after sensitizing exposure to foreign agent (antigen)
- Involves cellular and humoral immunity - T and B lymphocytes
- - B = humoral immunity --> antibodies
- - T = cellular immunity
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Monocytes
(non-granular leukocytes) (p.2-3)
- 4-8% of WBCs
- Not activated as monocytes.
- Migrate to tissue
- Activated as macrophages once in area of injury
- Important APCs - antigen-presenting cells
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Polymorphonuclear Leukocytes
(PMNLs)
- Found primarily in vascular system
- Constitute majority of circulating leukocytes
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Macrophages
- Have receptors for antigens, for complement components, and for FC receptors on antibodies
- Effective in stimulating immune system
- Also function as APCs
- Ingest foreign antigens, partially digest with lysosomal enzymes, then return portion of antigen to cell membrane so other immune cells can see it and further attack
- Generate superoxide free radicals and hydrogen peroxide
- Primary functions:
- - Phagocytosis
- - Antigen-presenting to T-helper cells
- - Cytokine production (IL-1, IL-6, IL-8, and several others)
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Neutrophils
- First to arrive at site of injury; Usually first seen with acute infection
- Main function = phagocytize microorganisms
- Granules contain enzymes that digest biologic materials and generate free radicals
- Destroy bacterial cell membranes
- Categorized based on maturity:
- - Segs = mature
- - Bands = immature
- Normal neutrophil count = 1500-7700 /uL
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Eosinophils
- Contain cytosolic granules of toxic enzymes – acid phosphatase and peroxidase
- Contain type of protein particularly effective against parasites
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Eosinophilia
- Increased eosinophils
- Hallmark of allergic reactions
- Seen with asthma, hay fever, eczema,allergic dermatitis, drug reactions, and parasitic infections
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Basophils
- Function – antigen interacts with IgE on basophil receptor (mast cells) --> cell’s granules --> histamine release --> bronchoconstriction, mucus production, pruritus, vasopermeability, vasodilation
- Allergic reaction, type I hypersensitivity
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What about T lymphocytes?
- Produced in bone marrow and mature in the thymus gland
- Acquire histocompatibility during maturation
- Must see foreign antigen, understand it, then replicate it (cellular immunity)
- Responsible for initiating cellular immunity
- T-cell precursors in bone marrow --> thymus gland --> cell division and maturation – acquire Histocompatibility molecules --> secondary lymph organs (appendix, tonsils, adenoids, Peyer’s patches in small intestines) --> react with antigens
- Increase in viral infections
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What are the 3 pools of neutrophils?
- Marginal – 1-4 days
- Circulating – 3-6 days
- Bone marrow – 9 days
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What is meant by bands versus segs in terms of the maturation of neutrophils? (p.3)
- Stages of neutrophil maturation – myeloblasts, promyeloblasts, myelocytes, metamyelocytes, bands, segmented neutrophils (segs)
- Bands = less mature than segs
- Degree of immaturity = different pathologies
- More immature the neutrophil = sicker the patient (i.e., chronic leukemia)
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What does a left shift indicate?
- Increased metamyelocyte / bands = typical left shift seen with bacterial infections
- Higher # of extremely immature neutrophils = larger left shift = sicker patient
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Review cell-mediated and humoral immunity. (p.1)
- Humoral immunity – B lymphocytes
- - Prevention*
- - Relies on production of antibodies by B-cells and plasma cells
- Cell-mediated immunity – T lymphocytes
- - Recovery*
- - Involves interaction of helper T cells and cytotoxic T cells with various target cells
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What immune cells are involved with each type of immunity?
- B-cell immunity – B lymphocytes
- - Produced and mature in bone marrow
- - Travel to lymphoid tissue
- - Once exposed to antigen, B lymphocytes turn into plasma cells that secrete specific antibodies.
- - Antigens are exposed to B cells once they are attached on T helper cells
- T helper cells are subsets of CD4 T-lymphocyte cells
- Without T cells, B cells cannot recognize antigen as foreign.
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