Immunology Flashcards
What is the innate immune system?
First line of defense against bacteria, viruses, and parasites RAPID response (min to hours) NON-SPECIFIC defense (attacks all foreign antigens in the same way) NO memory defense
Physical barriers are part of the ________ immune system
Innate (Natural)
Examples: Lysozyme in tears/other secretions Skin surface, fatty acids, and normal flora Rapid pH change between stomach/intestines Cilia in nasopharynx Mucus lining in trachea Stomach pH of 2 Normal gut flora Flushing of urinary tract
The complement system is a group of 30+ ________________ that activate in a cascade-like manner in response to _________.
30+ plasma proteins, in response to an antigen (anything foreign to body)
It enhances (“compliments”) the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism
Promotes inflammation to help clear infection
Attacks the pathogen’s cell membrane —> lysis
Sequence of events in the complement pathway
- Activation through either the classical, let in, or alternative pathways (most common)
- Formation of the enzyme C3 convertase (cleaves C3)
- Opsonization and phagocytosis
- Inflammation
- Membrane Attack Complext (MAC) formation and lysis
The three pathways of the complement system:
- Classical Pathway - triggered by antibodies (such as IgM and IgG) binding to an antigen; most responses use this pathway
- Lectin Pathway: lectin proteins bind to mannose residues on the microbial surface
- Alternative Pathway: complement proteins act directly on cell surfaces (unusual)
The most abundant complement protein is _______.
C3
C3 convertase cleaves C3 to activate the classical pathway
The coating of a microbe by an antibody (or complement protein) to “tag” it for phagocytosis is called:
Opsonization
Marks the cell for destruction
Phagocytosis is the mechanism by which host cells:
Engulf and destroy an organism (some phagocytes are better than others)
The final step in the classical pathway of the complement system is the formation of the _________________
Membrane Attack Complex (MAC) —> Lysis
MAC is a complex of complement proteins that form to cause the lysis of a microbe
C5b, C6, C7, C8, and C9 are the proteins that bind to form MAC
Once these proteins combine on the surface of an antigen, the cell wall disintegrates and cell rupture ensues
________________ is an autoimmune disease that is also a huge player in complement deficiencies
SLE
*Same deficiencies seen in pyogenic infections
C1,C2,C4 deficiency —> deficiency in cleanup of IC and activation of classical pathway
C3 deficiency —> inability of cleanup of IC, complement activation
Factor H deficiency —> loss of control in the activation of alternative pathway, low C3 concentrations
Stages of an inflammatory response
- Tissue Damage
- Chemical signals alert endothelial cells along the capillary wall
- Neutrophils become “sticky” and stop rolling along the capillary wall
- Mast cells release histamine
- Histamine causes vasodilation and openings in between endothelial cells
- Fluid and leukocytes enter the affect tissu
- Neutrophils “squeeze” through endothelium (“extravasation”)
- Neutrophils are attracted to the damaged site and ingest/destroy bacteria
*Neutrophils = professional phagocytes (monocytes = 2nd line)
Neutrophils, eosinophils, and basophils are _______________
Monocytes and Lymphocytes are _________________
Granulocytes; Agranulocytes
Granulocytes have granules (packets of histamine, lysosymes, etc to help breakdown things)
Monocytes are the most important agranulocytes
Never Let Monkeys Eat Bananas
The distribution of WBCs in descending order:
Neutrophils (62%) Lymphocytes (30%) Monocytes (5%) Eosinophils (2.5%) Basophils (0.5%)
All about the Neutrophils!
The most abundant WBC - the body’s first responders
Particularly active against bacteria
Adhere to the vascular endothelium using adhesion molecules
“Squeeze” out into the tissue to attack bacteria
Undergo phagocytosis very efficiently to kill antigens
Promote inflammation
Increased neutrophils on the WBC diff is suggestive of…..
An acute bacterial infection, particular if bands (immature neutrophils) are high
An increase in BAND neutrophils means that the bone marrow has been signaled to release more WBCs and can be described in lab values as LEUKOCYTOSIS WITH A LEFT SHIFT
______ signifies a “left shift”
> 8% bands (immature neutrophils)
Indicative of an acute bacterial infection
Typically, bands only make up 3-6%
Elevated neutrophil count is called …
Neutrophilia
Causes:
• Acute bacterial infection (also fungal, viral, parasitic, spirochete)
• Noninfectious inflammation (hypersensitivity rxn, postop state, acute gout
• Metabolic: DKA, uremia, preeclampsia
• Other: exogenous corticosteroids
Low neutrophil count is called …
Neutropenia
Defined by the absolute neutrophil count (ANC)
Causes: • Infection (esp VIRAL) • Bone Marrow disease • Radiation therapy • Chemotherapy drugs • Toxins • Hereditary
_____________ are WBCs that play a role in allergic and antigen response
Basophils
Release granules that contain:
- HISTAMINE (increases blood flow to area)
- Heparin (reduces clotting)
____________ target larger parasites (ie Helminths) that are too large for one WBC to phagocytize
Eosinophils
Modulate allergic inflammatory response (help the basophils)
Rare in blood but numerous in the mucous membranes of the respiratory, digestive and lower urinary tracts
__________ are early responders in Type I allergies
Mast Cells
Release histamine and heparin
Present in barrier tissues (mucosa)
Play important roles in allergy and ANAPHYLAXIS reactions (think Type I hypersensitivity)
Largest WBC
Monocytes
Found in the blood and SPLEEN
Monocytes migrate into the tissues to become:
• Macrophages
• Dendritic Cells
Why you get splenomegaly with a MONONUCLEOSIS infection
Monocytes are themselves agranulocytes but can differentiate into macrophages, which are granulocytes
The three different types of Lymphocytes
B-cells
T-cells
Natural Killer Cells
