Immunology Flashcards
body defence system
a system which combats and removes foreign cells/infectious agents (viruses, bacteria, fungi, parasites, toxins, cancerous cells)
what can foreign cells and infectious agents do to the host?
cause pathological damage and eventually kill their host if they are allowed to multiply unchecked
where are blood cells derived from?
either myeloid stem cell derived or lymphoid stem cell derived
3 types of blood cells
erythryocytes (red blood cells), platelets (megakaryocytes), and leukocytes (white blood cells)
types of leukocytes
neutrophils, eosinophils, basophils, monocytes, plasma cells & B cells, T lymphocytes, and NK cells
what are neutrophils, eosinophils and basophils also known as?
polymorphonuclear cells or granulocytes
where are the granulocytes and monocytes (and erythrocytes and leukocytes) derived from?
myeloid stem cells
where are plasma cells, B cells, T lymphocytes, and NK cells derived from?
lymphoid stem cell derived
what is the cellular component in immune response?
leukocytes (white blood cells)
general function of WBC
to provide a rapid and potent defense against any infectious agent
approximate number of WBC in adult human
7000 cells/µL
how can WBC count be used as a diagnostic tool to tell if there is infection present?
increased WBC count
where do WBC enter blood circulation from?
bone marrow or lymphoid tissue
how do WBC know where site of infection is?
chemotaxis - chemical messenger tells them where it is via attraction
movement of WBC from blood circulation to tissues occurs by
diapedesis - involves deformation of cells to pass through a small pore
what is the small pore in diapedesis mediated by?
molecules known as selectins
where does diapedesis occur?
only in the venous system (NOT ARTERIAL SYSTEM) - selectins are only present in inner part of endothelial cells of veins
how long do granulocytes circulate blood and exist in tissue?
once entered the blood, they spend 4-8 hours circulating; once in tissue, they exist for 4-5 days
how long do monocytes circulate blood and exist in tissue?
transit time of 10-20 hours in the blood; once in tissue, they enlarge (~ 5 fold) and become tissue macrophages (exist for months)
what happens to monocytes when they enter tissue?
they enlarge by 5 times and become tissue macrophages, existing in the tissue for months
how long do lymphocytes circulate blood and exist in tissue?
enter circulation continually from lymph nodes and circulate between tissues, lymphatic system, and circulation; life span of months or years
what are the 3 types of granulocytes?
neutrophils, eosinophils, and basophils
what do neutrophils do?
possess a number of antibacterial weaponry and have the ability to find bacteria/fungi and neutralize them by phagocytosis
first line of defense
most abundant leukocyte in blood
neutrophil
first defensive cell type to be recruited to a site of infection?
neutrophil
which granulocyte is mobilized following parasitic infection?
eosinophils
examples of parasitic infection
schistosomiasis and Trichinella “pork worm”
what do eosinophils do?
approach parasites and release substances that kill or weaken it such as hydrolytic enzymes; they also help detoxify inflammatory substances by releasing hydrogen peroxide
strongest oxidizing agent in the body (released by eosinophils)
hydrogen peroxide - breaks up bonds and detoxifies parasites and toxins
what is the circulating counterpart of tissue mast cells?
basophils
what do only mast cells produce?
heparin - used to prevent coagulation (anticoagulant) and facilitate removal of the fat particles
what do both basophils and mast cells do?
release histamine (and small quantities of bradykinin and serotonin) - important in allergic reaction (mediated by IgE)
what does bradykinin do?
activates the pain pathway (e.g., bee stings)
what does histamine do?
increase permeability of the cell, disrupts starling forces by increasing pore size so proteins can now move across membrane
where are basophils and mast cells located?
in circulation and in tissue, respectively
2 functional forms of immunity
1) innate immune system: first line of defense - normally sufficient to prevent disease
2) adaptive/acquired immune system: improved by repeated infection; involves specific response to the infectious agents
both neutrophils and macrophages are capable of
phagocytosis
examples of chemotactic factors
bacterial toxins, degenerative products of inflamed cells, complement complex, specific factors such as cytokines secreted by host or invading cells, foreign membrane protein triggering leukocytes
diapedesis is facilitated/initiated by
selectins and their ligands (adhesion molecules) which are present on the surface of leukocytes and endothelial cells of venous capillaries
when activated by chemotactic factors, what do selectins and ligands do?
cause leukocytes to slow down + make them sticky so they start rolling, which leads to diapedesis (searches for points to leave blood vessel to adjacent tissue)
what components make up the innate (natural) immune system?
physical barriers/factors, soluble compounds, cellular components
what are the physical barriers and factors in the innate immune system?
physical barriers: skin (most infectious agents cannot penetrate intact skin) - this is why people with burns/cuts get infections easily
physiological factors: pH, temperature, oxygen tension limit microbial growth, acids + digestive enzymes destroy ingested organisms
main routes of infections
epithelial surface of nasopharynx, gut, lungs, and genito-urinary tract
what are the soluble compounds involved in the innate immune system?
lysozyme, complement complex system, c-reactive protein, cytokines
lysozymes
enzymes that can attack bacterial cell wall (made of proteoglycan - splits the bond between N-acetylglucosamine and N-acetylmuramic acid
c-reactive protein
bind to surface of damaged cells and bacteria, promote the binding and activation of complement system
facilitate opsonization and recognition of bacteria leading to more efficient uptake by phagocytes
the complement complex system
system of ~20 serum proteins which interact in a cascade
what are the 3 pathways that can lead to complement activation?
classical pathway, alternative pathway, and the pathway involving Mannose Binding lectin on pathogen surface
how is the classical pathway activated?
by antibody-antigen complexes
how is the alternative pathway activated?
binding of complements to surface molecules of pathogens (don’t require antibodies)
what do all 3 pathways do to activate the complement cascade?
activate C3 convertase which activates the cascade
what are some functions of the complement complex system?
opsonization of bacteria, activation of mast cells and basophils, chemotaxis of white blood cells, and lysis of cells
cytokines
biochemical messengers stimulate leukocyte activity following infection - increase production of granulocytes, monocytes, and lymphocytes