Innate Immunity

Question 1

4 responsibilities of the innate immune system

Answer 1

1. control the colonization of non sterile niches in the body 2. prevent infections into sterile tissues by potential pathogens 3. mounting an immediate, generic response against infection 4. transporting antigens from the pathogen to regional lymph nodes

Question 2

types of barriers

Answer 2

mechanical (epithelial cells with tight junctions, longitudinal air/fluid flow, mucus movement via cilia); chemical (fatty acids:skin, low pH & enzymes such as pepsin: gut, salivary enzymes: mouth/nose, antibacterial peptides such as defensins: everywhere except the eyes/nose); microbial (normal flora in the gut and the skin)

Question 3

ways to breach barriers

Answer 3

1.microscopic trauma (bacterial invasions) 2. major trauma (soil) 3. vector transmission (malaria mosquitos)

Question 4

non-immunological barriers to infection

Answer 4

1. cough/gag reflex 2. normal flora 3. mechanical obstructions vs. normal urine flow or normal intestine peristalsis 4. mucociliary removal or respiratory secretions 5. low gastric pH (1)

Question 5

first responders to an epithelial barrier breach

Answer 5

macrophages, phagocytosis is usually sufficient

Question 6

inflammation

Answer 6

second response to a barrier breach: effector molecule delivery, local blood clotting, repair of damaged tissue. inflammation is mediated by cytokines and chemokines

Question 7

cytokines: types and general purpose

Answer 7

systemic effects: TNF-alpha, IL-1beta (activates IL-6), IL-6 (activates lymphocytes)
local effects: CXCL8 (neutrophils, basophils, T cells), IL-12 (call for lymphocytes)

Question 8

systemic response in the liver

Answer 8

acute phase protein creation (mannose binding lectin) –> activation of complement of opsonization

Question 9

systemic reaction in the bone marrow epithelium

Answer 9

neutrophil mobilization –> phagocytosis

Question 10

systemic response in the hypothalamus and fat/muscle

Answer 10

increased body temperature (via protein and energy mobilization in fat/muscle) —> decrease viral and bacterial replication, increased antigen processing, increased specific immune response

Question 11

PAMPs and PPRs

Answer 11

PAMP - pathogen associated molecular pattern (spatial organization and chemical structure), PRR - pattern recognition receptor found in the innate immune system (ex. MBL - mannose binding lectin - found in invading bacteria and not normally in host cells)

Question 12

toll like receptors

Answer 12

10 highly important PRRs capable of recognizing PAMPs that are present on most pathogenic microbes. some are found extracellularly (bacteria), and some in the nucleus (viruses)

Question 13

viral infections

Answer 13

mostly require the adaptive immune system to take care of the situation

Question 14

host cell specific defense to viral infection

Answer 14

via interferons (innate immune response). can be induced in almost any virus infected cell in the body. activated via the PRR sensors RIG-1 and MDA-5 found in the cytoplasm/cytosol of most cells that react to dsRNA long strands and cause the release of type I interferons IFN alpha, and IFN beta

Question 15

RIG-1 MDA-5

Answer 15

PRRs found in the cytoplasm/cytosol of most cells - responsible for initiating the innate immune response to viruses, recognize dsRNA (LONG STRANDS!) causes the release of Type I interferons IFN alpha and beta

Question 16

IFN-alpha & IFN-beta

Answer 16

type I interferons activated by RIG-1 and MDA-5 —> induce resistance to viral replication, increase MHC-C1 expression and antigen presentation, activates dendritic cells and macrophages, activates NK cells

Question 17

production of a Type I interferon

Answer 17

is a CRUCIAL initial innate immunity response to a viral infection

Question 18

dendritic cells

Answer 18

promote the initiation of an adaptive response in local lymph nodes

Question 19

primary and most immediate innate immune response to a virus infection occurs via

Answer 19

NK cells

Question 20

NK

Answer 20

develop in the bone marrow, are activated by type I interferons, lyse cells that have an abnormal number of MHC Class I receptors (presumably the decrease is due to down regulation by a virus that has taken over a host cell in an attempt to decrease the binding of MHC to CD8 killer cells). can slow down the virus in time for the adaptive immune response to kick in. recognizes abnormalities in cells