The Immune System MCAT

innate immunity

-composed of defenses that are always active but unable to target specific invaders

-nonspecific immunity

adaptive immunity

-specific immunity

-targets a specific pathogen

-slower to attack but retains memory of pathogens

bone marrow

-produces all leukocytes(white blood cells) that participate in the immune system

spleen

-location of blood storage and activation of B-cells, which turn into plasma cells to produce antibodies for adaptive immunity

humoral immunity

the division of adaptive immunity in the blood rather than cells

T-cells

-mature in thymus, small gland in front of the pericardium (sac that protects the heart)

-T-cells coordinate the immune system and directly kill viral infected cells

Lymph nodes

-provide a place for immune cells to communicate and mount an attack

Gut-associated lymphoid tissue

-immune tissue associated with the digestive system

-includes tonsils and adenoids, Peyer's Patches and lymphoid aggregates in the appendix

Leukocytes

-produced in bone marrow through hematopoiesis

-divided into granulocytes and agranulocytes

granulocytes

-contain granules that contain toxic enzymes and chemicals

-released by exocytosis

hematopoietic stem cells

gives rise to leukocytes, red blood cells and platelets

Agranulocytes

-includes lymphocytes and monocytes

lymphocytes

-responsible for antibody production and targeted killing of infected cells

monocytes

-phagocytic cells in the membrane

-become macrophages in tissues

defensins

antibacterial enzymes found on the skin

lysozyme

antibacterial enzyme found in tears and saliva

Gastrointestinal defense

-stomach secretes acid to kill pathogens

-large bacteria population in gut, when new bacteria enters, they need to compete

complement system

-a form of non-specific defense that consists of a number of proteins in the blood

-activated through classical pathway (antibody binds to pathogen) or alternative pathway, no antibodies

-the proteins punch holes in bacteria

interferons

-proteins that prevent viral replication and dispersion

-cells that have been infected by viruses produce these

macrophages

-agranulocytes that reside in tissue

-become a resident population in the tissue

-once activated it phagocytizes the invader through endocytosis

-then it digests the invader with enzymes

-lastly it gives little pieces of the invader to other cells using the protein major histocompatibility complex

MHC

-binds to pathogenic peptide and carries it to the cell surface to be recognized by cells of the adaptive immune system

cytokines

-chemical substances that stimulate inflammation and recruit additional immune cells to the area

MHC-I

-all nucleated cells in the body display these

-any protein produced in a cell can be loaded onto these and can be presented at the surface

-the pathogen is brought to the surface as a flag to show the cell is infected

-certain t-cells can then prevent the infection of other cells

MHC class II

-mainly displayed by professional antigen-presenting cells such as macrophages

antigen

a substance that can be targeted by an antibody

pattern recognition receptors

-present in macrophages and dendritic cells

-able to recognize the type of pathogen

Natural killer cells

-a non-specific lymphocyte that is able to recognize downregulation of MHC and induce apoptosis of the virally infected cell

Neutrophils

-a type of granulocyte, the most common leukocyte in blood

-very short lived, 5ish days

-phagocytic and target bacteria

-use chemotaxis to track down bacteria

chemotaxis

-the sensing of certain products given off by bacteria and migration of nucleophils to follow these products back to the bacteria

eusinophils

primarily involved in allergic reactions and invasive parasitic infections

-upon activation, they release large amounts of histamine, an inflammation mediator

-allows for more immune cells to move out of the bloodstream and into the tissue

basophils

-large purple granules

-involved in allergic responses

-least common leukocyte in the bloodstream

B-cell

-part of adaptive immune system

-Lymphocyte

-created and mature in bone marrow

-govern humoral responses

-produce antibodies

-mature in the spleen

-agranulocytes

T-cell

-lymphocyte in adaptive immune system

-created in bone marrow and matures in thymus

-govern adaptive responses

humoral immunity

-involves the production of antibodies

-may take as long as a week to become fully effective after initial infection

Immunoglobulins

-antibodies

-able to neutralize pathogens

opsonization

once an antibody binds to an antigen, it can attract other leukocytes to phagocytize the antigen

agglutinate

-antibodies may cause pathogens to clump together, forming large insoluble complexes that can be phagocytized

degranulation

-the exocytosis of granule contents caused by the binding of an antigen to antibodies on the surface of a mast cell

-releases histamine and causes an inflammatory allergic reaction

variable domain

the ends of the Y on the antibody

antigen binding region

at the ends of the variable domain

-must match with the shape of the antigen

hypermutation

-B-cells undergo this to find the best match for the antigen binding region of the antibody

naive B-cells

-b-cells that have yet to be exposed to there antigen

-stay in lymph nodes until needed

Plasma cells

-created by b-cells

-produce many antibodies to fight infection

memory B-cells

-produced by b-cells and remain in lymph nodes

primary response

The initial activation

-takes 7-10 days

secondary response

-if the same pathogen is encountered again, the immune response will be more rapid and robust

positive selection

-the maturing of only cells that can respond to presentation of antigen on MHC

-those that cannot are put through apoptosis

negative selection

causing apoptosis to cells that are self-reactive

-activated by proteins produced by the organism itself

thymosine

-a peptide hormone secreted by thymic cells that aids in the maturation of T-cells

Helper T-Cells (CD4+ T-cells)

-coordinate immune response by secreting chemicals known as lymphokines

-most effective against bacterial, fungal and parasitic infections

lymphokines

-recruit other immune cells and increase their activity

HIV (Human immunodeficiency virus)

-infection prevents the immune system from mounting an adequate response to infection

Cytotoxic T-cells

capable of directly killing virally infected cells by injecting them with toxic chemicals that promote apoptosis

memory T-cells

-lie in wait until next exposure at which time their reaction is more robust and rapid

self antigens

-the proteins and carbohydrates present on the surface of every cell in the body

-signal to the immune cell that the cell in not threatening

autoimmunity

-when the immune cell doesn't recognize that the cell is part of itself and attacks it

allergies

-when the immune system is hypersensitive to a non-threatening antigen

hypersensitivity reactions

autoimmunity and allergies

glucocorticoids

used to treat most autoimmune diseases

active immunity

the immune system is stimulated to produce an antibody against a specific pathogen

passive immunity

the transfer of antibodies to an individual

-effects only transient

lymphatic system

-a type of circulatory system

-contains one-way vessels that grow large as they move toward the center of the body

-the vessels cary lymphatic fluid (lymph) and join to compromise a large thoracic duct in the posterior chest

-drains remaining fluids from capillaries

lymph nodes

small, bean-shaped structures along the lymphatic vessels

-provide a space for the cells of the immune system to be exposed to possible pathogens

edema

-swelling due to fluid collection in tissue

-only occurs when lymphatic system is overwhelmed

Lacteals

-small lymphatic vessels used to transport fat from digestive system to blood

germinal centers

-area in which B-cells proliferate and mature in lymph nodes