chapter 42 - immunity

immune system

protection against pathogens

comprised of multiple organs and cells, each having a different role

pathogens

harmful organisms or viruses that cause disease

two major types of defense systems

1. innate/non-specific

2. adaptive/specific

innate/non-specific

always up and running/functioning, tries to protect against everything

adaptive/specific

needs to be activated, tries to protect against specific pathogens

has memory - activates quicker and stronger upon subsequent encounter with particular pathogen

innate/non-specific defense system

surface barriers

internal defenses

surface barriers

skin, mucous membranes

multilayered skin - normal flora “good bacteria” and secretions (salty, acidic, help suppress bacterial growth)

mucous membranes - mucus, lysozyme (breaks down bacterial cell wall & protects against gram positive bacteria), HCl (stomach)

mucous membranes

line digestive tract/passageways

line respiratory tract/passageways

line urogenital tract/passageways

ALL allow for access to outside world

internal defenses

phagocytes, NK cells, antimicrobial proteins, inflammation, fever

phagocytes

cells that engulf and digest foreign substances

ex: macrophages and neutrophils (carry out phagocytosis)

initial binding step is key

natural killer cells (NK)

contact and check cells

induce apoptosis in cancer or virus-infected (not 100% effective)

eosinophils

white blood cell

gathers around parasites

releases killing chemicals

inflammation

signaling molecule - leaky caps (increase blood flow) and recruit WBCs

4 cardinal signs

1. heat

2. swelling

3. redness

4. pain

fever

temporary increase in body temperature

increases speed of biochemical rxns

liver and spleen sequester iron and zinc

specific

looking for a particular pathogen

systemic

components are not localized to one place in the body

memory

if re-encounter the same antigen, then it can react quicker and stronger

HAS to be ACTIVATED

white blood cells

phagocytes

NK cells

eosinophils

neutrophils

two arms of specific immune system response

humoral and cellular

humoral

mediated by B lymphocytes/cells

produce an antibody based response or defense

cellular

mediated by T lymphocytes/cells

involves of a cell to cell response

generation of immune system cells

APC (antigen-presenting cell)

phagocytoses foreign invader - digests - displays fragments

stem cells

in red bone marrow

undergo cell division

differentiate or maintain line

progenitor lymphocytes

not fully mature

proliferate and differentiate to either B cells or T cells

B cells

1. plasma membrane: produce antibodies (ABs)

2. memory: B cells that will remain in the body long-term

   • these cells can activate more quickly; if re-exposed to the antigen

3. live about 3-5 days and then die

T Cells

1. Cytotoxic (T_c)

2. Helper (T_H)

3. Suppressor T cells

4. Memory cells

Cytotoxic (T_c)

do the cell-to-cell killing

Helper (T_H)

do communication among lymphocytes

Suppressor T cells

regulatory cells, tore down immune response toward end of infection

Memory T cells

these cells can activate more quickly; if re-exposed to the antigen

antigen

molecule that provokes immune response; usually foreign protein

could be sugar or lipid

could be protein from virus or pathogen

antigen challenge

bind SPECIFICALLY to the antigen

this neutralizes the antigen

non-active and active receptors proliferate

then differentiate into plasma cells and memory B cells

which create antibodies

antibody structure

immunoglobulins (Ig’s)

basic structure: 2 heavy chains (polypeptide, connected by disulfide bonds), 2 light chains

Fab region

antigen binding region

Fc (stem region)

binds to Fc receptor on certain cells

neutralization

antibody binds and masks dangerous parts of antigen

precipitation

antibodies crosslink antigens, take out of solution and enhances their phagocytosis

opsinization

antibodies serve as handles on antigens and pathogens

ENHANCES the initial binding phagocytosis

complement fixation

complement = family of proteins

pre-existing separately in blood plasma

enhances the insertion of MAC (membrane attack protein)

forms a pore

primary response

1st time response for this antigen

secondary immune response

1. stronger (higher antibody level)

2. faster (no lag)

3. longer-lasting (levels elevated longer)

basis for vaccines

weakened form of antigen (e.g. attenuated virus)

primary response - memory cells

maybe give booster

self-antigens

Major Histocompatibility Complex Proteins (MHC Proteins, exist on surface of all cells - i.d badge) & HLA (Human Leukocyte Antigen)

group of glycoproteins on surface of an individual’s cells

unique to each individual, identify cells as “self”

usually not reactive with self immune sys, but strongly reactive to foreign immune sys

two classes of self-antigens

1. class I MHC

2. class II MHC

class I MHC

found on surface of nearly all body cells

usually display peptides from breakdown & recycling of body’s own cellular proteins

class II MHC

found on surface of certain cells of immune sys

APCs = antigen-presenting cells (dendritic cells, macrophages, B cells)

if dendritic cell…

exception: can have non-self antigen MHC I

why undergo apoptosis?

1. cancerous cell: proteins are mutated

2. autoimmune disease: can’t distinguish self for non-self

3. failure of positive or negative

4. viruses: viral protein fragments, abnormal cell

perforin

protein released by T_c

inserts into membrane of target cells and makes pores

granzyme

enzyme that breaks down proteins in target cell

causes apoptosis

induce target cells to undergo apoptosis

central role of T_H cells

autoimmune disease

when fails to distinguish from self v non-self

over 100 of them

immune systems attacks own cells

type I diabetes

insulin dependent, autoimmune disease

immune system attacks and wipes out bet cells in pancreas

insulin released, peptide hormone

rheumatoid arthritis

autoimmune disease

infection and one agent have peptide sequence

immune system attacks joints

multiple sclerosis

autoimmune disease

immune systems attacks myelin sheath in neurons

myelin sheath

helps with insulation

no insulation = slows down signals, base axons have short circuiting

prednisone

fat and water retention, loss of bone mass

dexamethasone

stimulates suppressor T cells

allergies

not autoimmune

allergens = antigens that provoke an allergic immune system response

MADGE (different classes of antibodies)

IgM

IgA

IgD

IgG

IgE

histamine

causes leaky capillaries

increase mucous, trying to flush out

smooth muscle constriction

HIV

human immunodeficiency virus

causes AIDS

infect macrophages (integrates viral DNA into host DNA)

production, assembly, exit - doesn’t hurt macrophages

eventual mutation of HIV coat protein (gp120)

makes virus able to infect T_H cells - exiting kills T_H cell