mmi 188 midterm 1

purpose of immune system

1. recognition of foreigners 2. prevention of spread 3. clearing of invaders 4. healing body

Antigen

is the target of an adaptive immune response

Immunogen

induces an adaptive immune response (want to make antigen more immunogenic)

adaptive immune response

1. humoral 2. cell mediated

Humoral immunity

antibodies and associated accessory

systems

Cell-mediated immunity

T lymphocytes and associated

accessory systems

involved in both parts of the adaptive

some parts of innate like complement and cytokines

colicins

compounds secereted by bacteria that kill other organisms

commensal flora

enhance human nutrition by digesting food and making vitamins

what happens when commensal bacteria die

-pathogenic bacteria gain foothold, produce toxins that hurt mucosa, red and white blood cells leak into gut between epithelial cells

pathogen

organism with potential to cause disease

Innate immunity

involves:

-physical barriers

-nonspecific responses to foreign invaders followed by destruction

complement system

1. bacteria activates and induces cleavage of complement protein

2. one binds to bacteria, the other to the effector cell

3. complement receptor binds to fragment on bacteria

4. bacteria engulfed and broken down in phagosome

(basically attaching bigger protein to antigen to have it recognized, works with antibodies too)

inflammation

1. surface wound introduces bacteria, which causes effector cells in surface to secrete cytokines

2. cytokines cause vasodilation, greater vasopermeability allows inflammatory cells in circulation to leave and enter tissue

3. infected tissue is heated, swollen and painful as inflammatory cells kill bacteria

innate

1. rapid response, fixed, limited number of specificites, constant during response

-mehcanical, chemical and microbiological barriers

adaptive

slow response, variable, highly selective specificites, improve during response

clonal selection

activation of lymphocytes by pathogen

-self reactive cells deleted

-cells that recognize foreign antigens remain and differentiate following exposure

• Immunological memory

• faster

and stronger second reaction to

pathogens

B cells

• become Plasma cells that secrete antibodies

T cells

• helper and cytotoxic

Dendritic cells

-In tissues act as cellular messengers that call up an adaptive immune response when needed.

-Migrate from tissues to lymphoid organs to deliver antigens from

pathogens. They are antigen-presenting cells (APC).

lymphocytes

B cells and T cells

Neutrophil

• phagocytic, small, short life, white pus, most common cell

-large reserves stored in bone marrow until needed to fight infection

-released where they engulf and kill bacteria

Macrophage

• phagocytic, large, long life

Ø first to detect infection

Ø secretes cytokines that recruit neutrophils and other leukocytes

Ø APC

Eosinophil

• parasite killer.

Ø In allergy, activated eosinophils secrete enzymes that damage the

respiratory epithelium.

Ø They also release active oxygen that injures cells.

Parasite control trio

(mast cell, eosinophil, basophil) now associated with allergy.

Megakaryocyte

• platelet producer

Hematopoiesis

The generation of cellular elements of blood:

-Red blood cells

-White blood cells

-Platelets

-self renewing

bacterial binding on macrophages

macrophages have receptors that when bacteria bind induce:

Ø engulfment for degradation (phagocytic receptors)

Ø transcription and production of inflammatory cytokines (signaling receptors)

antibody

secreted form of B cell receptor

neutralization

When antibodies bind

to a bacterial toxin and neutralize its

toxic activity by preventing the toxin

from interacting with its receptor on

human cells.

opsonization

When a bacterium is

coated with IgG antibodies the

constant regions point outward and

can bind to receptors on a

macrophage, which then ingests and

degrades the bacterium.

how antibodies fight infection

1. neutralization

2. opsonization

Primary

lymphoid tissues

Ø Bone marrow

Ø Thymus

Secondary

lymphoid tissues

Ø Spleen

Ø Lymph nodes

Left subclavian vein

lymph returns to blood

Lymphocytes that encounter

pathogens in lymph nodes

stop circulating

draining lymph nodes

serve as specialized meeting

places for circulating lymphocytes and pathogens

Lymph nodes

highly organized and dynamic structures

that optimize interactions of lymphocytes and pathogens

Activation of adaptive immunity in the draining lymph node

-During an infection, lymphocytes proliferate in lymph nodes, resulting in swollen or enlarged lymph nodes

-pathogens and dendritic cells carry them come to afferent lymph draining infection.

-The dendritic cells specifically stimulate the division

differentiation of pathogen-specific small lymphocytes into effector lymphocytes

-some helper T cells and cytotoxic T cells leave in the efferent lymph and travel to the infected tissue via the lymph and blood.

• Other helper T cells remain in the lymph node and stimulate the division and differentiation of pathogen-specific B cells into plasma cells

-Plasma cells move to the medulla of the lymph node, where they secrete pathogen-specific antibodies, which are taken to the site of infection by the efferent lymph and subsequently the blood.

-Some plasma cells leave the lymph node and travel via the efferent lymph and the blood to the bone marrow, where they continue to secrete antibodies.

Spleen

: has aggregations of lymphocytes similar to those in lymph nodes

red pulp

is where old or

damaged red cells are removed