Immune System

Immunology

Study of the physiological mechanisms that allow the body to recognize materials as foreign and to neutralize or eliminate them

Function of the immune system

To protect the Boyd from a variety of harmful substances (allergens, toxins, malignant cells, pathogenic microorganisms)

Immune system

A group of cells, molecules, and organs that act together to defend the body against foreign invaders that may cause disease

Pathogen

A disease-causing agent

Antigen

Any foreign substance in the body that does not have the characteristics cell surface markers of that individual and is capable of eliciting an immune response (toxins, bacteria, foreign blood cells, and the cell of transplanted organs)

Epitope

The specific portion of an antigen that elicits an antibody response…the more epitopes…the greater the antibody response

Antibodies: Regions

Each antibody is made up to two identical heavy chains and two identical light chains, shaped to form a Y. (Variable and Constant region)

Antibodies

Protective proteins produced by the immune system in response to the presence of antigens (a part of immunoglobulins)

Types of Antibodies (Immunoglobulins)

IgG, IgD, IgE, IgA, IgM

IgG

Majority of antibodies to infectious agents, able to enter tissue spaces, works by coating microorganisms and speeds their destruction

IgD

On B lymphocytes, these are thought to somehow regulate the cell activation

IgE

Allergic reactions and parasitic disorders, usually only present in trace amounts

IgA

(Doublet) present on mucosal surfaces, guards the entrances to the body

IgM

(Star-shaped) initial antibody produced on first exposure to antigens, tends to stay in the bloodstream

Lymphatic System

The organs of the immune system are connected with one another and with other organs of the body by both blood and lymphatic vessels

Lymph Nodes

Clusters of small, bean-shaped structures primarily found in the neck, armpits, abdomen, and groin

Cells of the Immune System

Neutrophils. Eosinophil, Basophil, Monocyte, T-cell, B-cell, Natural killer, Macrophage

Myeloid Precursors

Neutrophils, Eosinophils, Basophils, Monocytes, Macrophages, Mast Cells, Platelets

Leukocytes

Neutrophils, Eosinophils, Basophils, Monocytes, Lymphocytes

Neutrophils

Directly kill and engulf bacteria (phagocytosis)

Eosinophils

Fight particular invaders, associated with allergy responses (also fight parasites)

Basophils

Involved in the inflammation process, release histamine

Monocytes

Immature Macrophages, engulf larger particles and then release a chemical messenger triggering T cells

Lymphocytes

A subtype of leukocyte

Mast cells

Found in mucous membranes and various connective tissues, release cytokines, heparin, various enzymes, histamine, growth factor, serotonin, eicosanoids, and PAF

Mast cell Activation

IgE antibodies, cytokines, and complement

Lymphoid Precursors

Develop into lymphocytes, and response later during an infection

T Lymphocytes

Are regulators, contain helper and suppressor cells, provide cell mediated immunity, and mature in thymus gland

B lymphocytes

Produce antibodies and respond to the T helper or suppressor cells, provide humoral immunity, mature in bone marrow

Natural Killer Cells

Directly kill viruses, microbes, and certain tumors, it is part of the innate immune system

Dendritic Cells

Act as antigen-presenting cells, capture and process antigens to activate T cells, play crucial role in initiating adaptive immune response

WBC lifespan: Granulocytes (Neutrophils, eosinophils, and basophils)

Short lived (2 to 3 days)

WBC Lifespan: Monocytes and Macrophages

Can live up for months (or possibly years)

WBC Lifespan: B cells

Short lived (2-3 days), but memory B cells can live for years

WBC Lifespan T cells

Variable, some memory T cells live for years

Immune response

Natural protective mechanisms of the human body, several lines of defense (physical, blood borne)

Recognition (phase of immune response)

The immune system identifies pathogens through receptors on immune cells, this phase involves he detection of antigens

Activation (phases of immune response)

Once a pathogen is recognized, immune cells become activated, this includes the activation of T cells and B cells in the adaptive immune response

Response (phases of unable response)

The immune system mounts a defense against the pathogens, this can involve the destruction of infected cells, neutralization of pathogens, and recruitment of additional immune cells

Resolution (phases of immune response)

After the pathogen is cleared, the immune response winds down, regulatory mechanisms help return the immune system to a resting state

Memory (phase of immune response)

Some immune cells remain as memory cells, allowing for a quicker response if the same pathogen is encountered again in the future

Innate: 1st line of defense

2 components: skin/mucosal barriers (physical barriers), nonspecific inflammatory response that takes place shortly after an injury or infection, no memory

Innate immunity

Immediate response, non-specific, physical and chemical barriers, cellular components, and inflammatory response

Acquired/Adaptive: 2nd line of defense

2 components: active and passive; specific response and as the potential for memory, recognizes and destroys foreign substances, immunity results from the development of antibodies in response to the presence of an antigen

Active acquired immunity

Active acquired immunity; person forms antibodies

Natural active acquired immunity: infected with organism and produced antibodies sufficient to offer future protection

Artificial active acquired immunity: inoculated with antigen and body produces antibodies

Major Histocompatibility Complex (MHC)

The key to proper functioning of the active: immune system is to be able to distinguish self from non-self

MHC proteins

HLA (human leukocyte antigen): distinct guiros our cells as self

Set of unique markers on human cells

Immunity

Physiologic mechanism that allows the body to recognize materials as foreign and to neutralize or eliminate them

Self vs. non-self

Self: proteins and other molecules, that are part of, or made by, the body

Non-self: not part of the body and recognized as potentially harmful (bacteria, viruses, parasites, pollen, dust, and toxic chemical)

Cell-mediated immunity

Involves T cells, particularly cytotoxic T cells and helper T cells, targets infected cells, cancer cells, and foreign tissues, effective against intracellular pathogens like viruses and bacteria

Humoral immunity

Involves B cells and the production of antibodies, targeted pathogens in body fluid (extra cellular pathogens), effective against extra cellular pathogens like bacteria and toxins

Cell-Mediated Immunity: T cells

Can recognize hidden organisms, when exposed to antigens they from sensitized T cells which provide immunity, have regulatory function, ore effective with viral infections

Cell-Mediated Immunity: Helper T Cells

Some T cells regulate the workings of the overall immune response, needed to activate many of the immune cells, including B cells and other T cells

Cell-Mediated Immunity: Cytotoxic T cells

Directly contact infected cells and destroy them, help rid the body of cells that have been infected by antigens as well as cells that have been transformed by cancer, responsible for the rejection of tissue and organs grafts

Regulatory T cells

Signal a stop to the immune process

Humoral Immunity: B cells

Produce a protective protein (Immunoglobulin) which has a receptor (an antibody) to a specific antigen, most effective against organism that are free floating easy to reach, particularly useful in fighting bacterial infections

Antigens Receptors

Both B cells and T cells carry customized receptors molecules that allow them to recognize and respond to specific targets

Isotype Switching

The first antibodies produced in a humoral immune response are IgM, but activated B cells can undergo isotype switching or class switching to secrete antibodies of different isotypes: IgG, IgA, and IgE

“Memory” Cells

Whenever T cells and B cells are activated, some become “memory” cells

Cytokines types

Pointe chemical messengers secreted by immune system cells

Types: Lymphocytes (secrete lymphokines), Monocytes and macrophages (secrete monokines), T-cells secrete interleukins (messenger between. Leukocytes)

Complement System

Part of the humoral immune system that helps or complements the ability of antibodies and phagcytuc

Classics Cascade Complement

Series of about 25 proteins that works to “complement” the work of antibodies in destroying bacteria

Passive Acquired immunity

Person receives antibodies

Shorter lived, but acts immediately

Natural passive acquired immunity

Transmission of antibody maternally, through breast milk or colostrum

Artificial passive acquired immunity

Antibodies produced in a lab are inoculated

Ex: treated with tetanus antibody

Natural Passive Immunity

While the fetal immune system is developing, the fetus is protected by antibodies that cross the placenta from the maternal blood to the fetal blood in the last trimester, and later via breast milk

Aging and the Immune System

Exterior defenses (affected by thinning of the skin and mucous membranes as well as decreased acid in the gut)

Phagocytes (show decreased function)

Eosinophils (accumulate in fewer number at sites of infection)

Basophils (release less histamine and heparin)

B and T cells (decrease in antibody production)