IMMUNOLOGY I Flashcards
(49 cards)
Define Antigen
Antigens are anything that causes an immune response.
Eg. bacteria, viruses, fungi, parasites, or smaller proteins that they express (aka “pathogens”).
Antigens are like a name tag for each pathogen that announce the pathogens’ presence to your immune system.
Some antigens are general, whereas others are very specific.
A general antigen signals “danger!”
A specific antigen signals “I’m a bacteria that will cause an infection in your lungs!” or “I’m HIV”
Define Antibody
An antibody (immunoglobulin or Ig) is a protein molecule created by our immune system to target an antigen for destruction. These proteins bind to the foreign antigen, thereby disabling the antigen and “tagging” it for destruction by other immune defenses.
Define Cytokines
CYTOKINES are cell-to-cell communication proteins that control cell development, differentiation, and movement to a specific part of the body. They are produced by a variety of leukocytes.
Define Interleukins
Interleukins (ILs) are 13 cytokines that are regulators (in part) of immune responses, inflammatory reactions, and hematopoiesis
interleukin 1 and 6 are responsible for what?
fever
Interleukin 6 causes what?
acute-phase response
Tumor Necrosis Factor (TNF)
Tumor Necrosis Factor (TNF) activates neutrophils, mediates septic shock, causes tumor necrosis.
Chemokines
Chemokines are a type of cytokine released by infected/injured cells. They initiate an immune response (signal circulating neutrophils and macrophages), and warn neighboring cells of the threat.
Interferons (IFN)
Block virus replication. Alpha, beta and gamma subtypes (IFN-α, IFN-β, IFN-γ)
IFN-γ is the strongest IFN, is produced by T cells, and activates macrophages, natural killer cells, and neutrophils
Type I Interferon
Type I includes the (α) & (β) forms
Function is to induce viral resistance in cells
Type I IFNs can be produced by almost any cell type in the body
Type I IFNs- friend or foe?
Has been shown under some circumstances to suppress T-cell responses and memory T-cells; this is important, especially in HIV
May interfere with bactericidal mechanisms
In influenza, it limits viral replication but creates pathologic inflammation in the lung
Type II Interferon
Type II is the (γ) form.
Type II interferon is secreted only by natural killer cells and T lymphocytes;
Its main purpose is to signal the immune system to respond to infectious agents or cancerous growth.
Explain divisions of immune system
Innate
aka ‘natural’, ‘non-specific’
FAST
Adaptive
aka ‘specific’, ‘humoral’ or ‘cell-mediated’
SLOW
HOWEVER, there is some crossover between the functions of the two branches!!
Hematopoiesis
The formation and development of the cells that make up “blood”
Embryo and fetus : occurs primarily in liver, spleen, thymus;
Birth –adult: occurs primarily in bone marrow small amount in lymphatic tissues
Innate Immunity
Components: Physical barriers Granulocytes (aka PMNs) Monocytes Macrophages Dendritic Cells Natural Killer Cells Complement Cascade
Characteristics
IMMEDIATE
Non-Specific Response…no memory
Response does NOT increase
with repeat exposure
First level of protection: Physical Barriers
Skin Protects against invasion Acidic pH of sweat Fatty acids and enzymes from pores/follicles Mucous Membranes Tears Saliva Mucus All contain lysozyme….which protects against gram (+) bacteria Gastric secretions…external? Yes! Acidic pH Commensal bacteria- “normal bacterial flora” Microbial Antagonism Both external and internal Compete with potential pathogens Upset by antibiotic use Example: vaginal candidiasis resulting from change in lactobacillus and/or G. vaginalis concentrations
When the barrier (first level of protection) isn’t sufficient protection: the inflammatory response
Damaged tissue and/or cell mediated histamine, prostaglandin and leukotriene release causes vasodilation and leaky capillaries
Cell mediated heparin release causes decreased clotting
RESULT: Increased blood flow to area, immunologic factors leak out of capillaries into interstitial space to do their jobs……
Adhesion molecules
Membrane proteins that connect cells to other cells or the extracellular matrix (ECM)
Play a major role in the recruitment of neutrophils to the site of inflammation…. neutrophils “roll” along the luminal surface of blood vessel towards the site of injury, then squeeze out between cells of capillary wall.
Chronic inflammation chronic cytokine release & leukocyte infiltrationrelease of lysozyme & free radicals tissue damage
Mutations in genes encoding cell adhesion molecules cause (we think) a variety of disorders vascular system (atherosclerosis?), skin, kidney and muscle, and the immune and nervous systems (Alzheimer’s disease? Autism?)
Basophils
Least common Mature in bone marrow Circulate in bloodstream Allergic & helminth responses Release histamine & heparin Reduction of clotting & increased blood flow resulting from vasodilation
Eosinophils
Derived from the bone marrow…usually 1-6% of circulating WBCs
Both circulating in bloodstream & present within organs… particularly the GI tract and respiratory tract
Release H2O2 and other oxygen radicals to kill microbes:
Viruses, parasites (esp. helminths)
Release leukotrienes- lipid signaling molecules that causes airway smooth mm contraction
Active in allergic reactions, asthma
Stimulate T-lymphocytes
Act as “antigen presenting cells” (APCs)
Weakly phagocytic
Neutrophils
Most abundant of the granulocytes
Circulate in the bloodstream
One L of blood contains about five billion neutrophils!
“First Responders”
particularly active against bacteria & fungi
Arrive within minutes of injury
Chemotaxis- neutrophils respond to chemokines
In turn release other cytokines to recruit monocytes & macrophages
Strongly Phagocytic
Neutrophil Extracellular Traps (NETs)
‘throw out’ extracellular fibers that bind bacteria
Mast Cells
Release histamine and heparin causing inflammatory cascade
Leave the bone marrow as immature cells, mature in tissues
Present in tissues that are boundaries b/t “inside” and “outside” (esp. mucosa)
Will degranulate if:
Injured
Encounters antigen or allergen
Exposed to complement proteins
Massive release of histamine results in anaphylaxis
Body-wide vasodilation leads to edema, decreased BP etc.
Monocytes
“agranular”
Give rise to dendritic cells & macrophages
Develop in bone marrow; half are stored in the spleen, half migrate to tissues and differentiate into dendritic cells and macrophages
Monos, Macros and Dendros have 3 primary functions:
Phagocytosis
Antigen presentation (APCs)
Cytokine production
Dendritic Cells
The ‘strongest’ of the APCs- best at activating helper-T lymphocytes
Antigens are captured by dendritic cells
The dendritic cell then migrates to the nearest lymph node & presents the antigen to T Cells and B Cells
Specialized dendritic cells in skin
Langerhans cells*
Macrophages
Large phagocytes
release TNF and Interleukins (ILs)
Also act as APCs
Present under the skin, lungs, GI tract and most other tissues
Macrophages have 3 stages of readiness
a) resting = cleaning up cellular debris (scavengers)
b) primed = more active engulfing of bacteria, display fragments of bacteria for T cells (act as APCs)
c) hyper-activated = inflammatory cytokines cause macrophages to enlarge and start rapidly destroying pathogens and/or cancerous cells
After digesting a pathogen, a macrophage will present the antigen to a helper T cell.
Antigen is integrated it into the cell membrane and displayed attached to an MHC class II molecule (MHCII)
The MHCII indicates to other white blood cells that the macrophage is not a pathogen, despite having antigens on its surface
