Host defenses

what are innate defenses

“first barriers”

properties of the normal host, non-specfic defenses

what are adaptive defenses

induced by the infection, specific to the pathogen

antigen based

what does the normal microbiome do

competes for attachment sites and nutrients, secretes bacteriocin

what are antimicrobial substance

fatty acids, lysozymes, antimicrobial peptides (AMPs), antibodies

what do AMPs do

make pores in the bacterial membrane to limit its efficacy

what are the innate defenses of the airways

mucous membrane will push out and trap bacteria

cilia cells remove the mucous and trapped bacteria

innate defenses of tissues/internal fluids

“second line of defense”

types: complement system, phagocytes, inflammation

what is the complement system

set of blood proteins that complement the action of antibodies

activation results in a Membrane Attack Complex (MAC)

how is the complement system activated

by antibodies (classic)

microbial cell wall components (alternative)

what kind of bacteria does the MAC work on

some gram-

no gram+

because it needs to attach to the outer membrane. if a gram- bacteria has a capsule it will also be resistant

what are monocytes

type of WBC

circulate in the bloodstream, attracted to inflamed tissues

differentiate into macrophages in tissues

phagocytic

what are granulocytes

cytoplasm contains granules

several types (eosinophils, basophils, neutrophils - phaogcytic, mast cells)

what are the two types of lymphocytes

B cells (antibodies)

T cells (helper and cytotoxic types)

what are the steps of phagocytosis

1. attachment of the organism to the membrane of the phagocyte

2. ingestion: the organism becomes enclosed in the phagosome

3. a) granules containing hydrolytic enzymes fuse with the phagosome and make phagolysosomes or b) oxidative burst: production of reactive oxygen species

   1. killing and digestion of the microorganism

what are the main types of cell that carry out phagocytosis

neutrophils and macrophages

what is the function of inflammation

allows recruitment of immune cells to the site of infection and increases concentration of molecules like antibodies

inflammation role of hormone Interleukin-1

reduces inflammation and increases movement of fluid and immune cells into the tissues

brings antibodies and proteins to the site

increases available cells for phagocytosis

how do fevers work

macrophages sense endotoxins

induce production of fever molecules (Interleukin-1)

Il-1 acts on brain to increase body temperature

Il-1 activates phagocytosis and other immune responses like inflammation

what do adaptive defenses rely on

detection and response to foreign antigens

recognition by the immune system

previous infection

what are the cell types of the adaptive immune system

B cells, T cells, antigen presenting cells (macrophages, dendritic cells)

T cell and B cell specficity and stuff just look at the slide

T helper cells

activate B cells and macrophages

Cytotoxic T cells

kill host cells that display foreign antigen on their surfaces

how do APCs and T cells work together

APCs bring the antigen to T cells

if the T cell is specific to that antigen, it will activcate and produce interleukin 2 to induce multiplication and differentiation in effector T cells and memory T cells

what is the major histocompabtibility complex (MHC) I

expressed by all cells, present antigen that comes from inside the cell

important role during infection

recognized by cytotoxic T cells

what is the major histocompabtibility complex (MHC) II

expressed by APCs and B cells

present antigens processed in the phagolysosomes

recognized by helper T cells

what do cytotoxic T cells do

kill specific foreign antigens

releases perforins and granzymes to kill the cell

useful in infections by virus/intracellular pathogens

what happens after a helper T cell activates a macrophage

they increase phagocytic activity and produce higher levels of hydrolytic enzymes

important role against bacterial pathogens

what are B cells

group of related proteins

they have variable binding sites

the part of them that don’t change binds to macrophages and activates the complement pathway

what are the different types of antibodies

IgA, IgG, IgM, IgE

activation of B cells

see slide

what is the function of antibodies

as opsonins which increase phagocytosis efficiency

bind to toxins, preventing their binding to host cells

bind to adhesins to prevent the binding

what is the purpose of memory cells

remember the antigen so that the immune response to a second exposure is faster and stronger

what is active immunity

involves the production of memory cells in response to antigenic stimulus

natural: following infection

artificial: vaccination

what is passive immunity

involves the acquistion of preformed antibodies

natural: placental transfer or colostrum

artificial: serum from an immune animal

what is natural immunity (species resistance)

incompatibility of the virulence factor with teh genetics of a certain species

why some species have diseases that cannot be transferred to other species