Adaptive (Specific) Immune System Physiology: Part 1- Gonsalves

One of the key differences between the adaptive and the innate defenses

the ability of the specific immune system to remember specific paathogens

The adaptive immune response is:

antigen-specific, systemic, and has memory

The cooperating defenses (branches) of the adaptive

cellular defenses and humoral immunity

Humoral immunity

specific immunity produced by B cells that produce antibodies that circulate in body fluids in the interstitial spaces

Antigens

large signaling molecules not normally found in the body. Substances that can mobilize the immune system and provoke an immune response.

General characteristics of Adaptive Immune System

1. Specific so that it can eliminate with equal precision almost any type of pathogen

2. Functional system

3. Must be primed by an initial exposure to a specific foreign substance called an antigen, takes time

The functional system

1. eliminates specific foreign substances as well as abnormal body cells

2. can magnify the inflammatory response and is responsible for most complement activation

Experiments in the late ___________ found that there were __________ __________ in the blood that _______________ against future ____________ by the same pathogen

1800s, protective factors, protect, infection

Experiments in the 19th century discovered that protective factors called _______________ could be

antibodies, transferred to other organisms that were not exposed to the antigen

Antibodies are

proteins that protect you when an unwanted substance enters your body

Antibodies are produced by

lymphocytes or their offspring

Three types of lymphocytes offspring

T cells, B cells, NK cells

Cellular immunity targets

virus or parasite infected tissue cells, cancer cells, foreign graft cells

How does cellular immunity target

can act directly by lysing foreign cells or indirectly by releasing chemicals that enhance the inflammatory response or activate other lymphocytes or macrophages.

Cellular immunity is carried out by

lymphocytes themselves

Antigen help distinguish

self from non-self

Large complex molecule that are NOT normally present in the body

antigens

Complete antigens have

Complete antigens are like a double threat in the immune system - they have the ability to provoke an immune response (immunogenicity) and also react with specific antibodies (reactivity). It's like a villain who can both incite a superhero's attention and directly engage in combat with them.

IMMUNOGENICITY and REACTIVITY

Immunogenicity

Immunogenicity is like a superhero power that allows an antigen (like a villain) to activate special cells (lymphocytes) and create antibodies (like an army) to fight against it.

Reactivity of antigen

the ability to react with lymphocytes and antibodies

Antigens include:

Nearly all foreign proteins, nucleic acids, lipids, and many large polysaccharides

_______________ are the strongest antigens

Proteins

Other antigens can include

pollen grains or microorganisms

Generally molecules like ______, ________, and many __________ are not immunogenic. They can ________ with other substances and become immunogenic. (Haptens)

peptides, nucleotides, hormones, link

Haptens

small molecules that are reactive but not immunogenic unless attached to a protein carrier.

The part of an antigen that is immunogenic

antigenic determinant

What binds to the antigenic determinants?

free antibodies or activated lymphocytes

A single antigen can have a variety of __________ _________ and _____________ many different kinds of antibodies.

antigenic determinants, stimulate

Large simple molecules that have many regularly repeating units, meaning they're not chemically complex are _____________.

not very immunogenic

Immunogenic

the ability of a molecule to solicit an immune response

Self-antigens

not foreign to us, but is foreign to other individuals

MHC proteins

Major Histocompatibility Complex- Cell surface glycoproteins whose main function is to present intracellular peptide fragments to T lymphocytes and mark the cell as it self or foreign.

MHC proteins have millions of different _______________ of ______________ making it unlikely that anyone except __________ ____________ will have the same MHC makeup.

combinations, genes, identical twins

Types of MHC

Class I and Class II

Class I MHC

these glycoprotein molecules are expressed on the cell surface of almost all nucleated cells and present peptide fragments derived from intracellular proteins.

Class II MHC

proteins are expressed primarily on antigen-presenting cells, including dendritic cells, macrophages, and B cells (cells that act in the immune response)

Types of cells in the adaptive immune system

B-cells, T-cells, APCs

B-cells are

involved in the humoral immunity

T-cells are

involved in cell-mediated immunity

APCs

antigen presenting cells do not respond to specif antigens but play an auxillary role (immune cells that specialize in presenting an antigen to a T-cell)

Lymphocytes originate from

hematopoietic stem cells in red bone marrow

When released from the bone marrow immature lymphocytes are

identical

Determination on what type of lymphocyte the immature lymphocyte will be is based on

where in the body it becomes immunocompetent

Immunocompetent

able to recognize a specific antigens by binding to and acting against it

T-cells are formed in

the thymus (2-3days) and are selected for their ability to identify foreign antigens

Negative selection

lymphocytes that strongly attack self-antigens are destroyed in the thymic medulla (their antigen receptors bind strongly to self)

Positive selection

weakly anti-self T-cells continue to develop and the ones that can best recognize self when attached to antigens are identified. This occurs in the thymic cortex.

When forming in the thymus lymphocytes

develop self-tolerance and immunocompetence

In the bone marrow B-cells become

immunocompetent and self-tolerant

Anergy in B-cells

when self-reactive B-cells are inactivated

Primary lymphoid organs

bone marrow and thymus. where B lymphocytes & T lymphocytes mature

Secondary lymphoid organs

spleen and lymph nodes and all other lymphoid organs

Immunocompetent lymphocytes display receptors that

bind to specific antigens

Immunocompetent lymphocyte's have _______________ receptors that are all __________ meaning these cells are _____________

10-100 thousand, identical, committed

Lymphocytes become ____________ before meeting the ____________ they may later attack.

immunocompetent, antigens

Genes, in reference to lymphocyte specification, determine

which specific foreign substances our immune system will be able to recognize and resist

Where do immature lymphocytes that are immunocompetent go

lymph nodes, spleen, and other lymphoid organs where encounters with antigens occur and they become fully functional B and T cells

Antigen Presenting Cells (APCs)

engulf particles and presents fragments of these antigens on their own surfaces where they can be recognized by T cells

Major types of APCs

Dendritic cells, macrophages, and activated B cells

Dendritic cells types and location

1. Langerhans cells mainly in the epidermis

2. dermal dendritic cells in the dermis

3. interstitial cells of connective tissues

These are 65-85% of bloodborne lymphocytes

T cells

APCs secrete proteins that activate __ ________ and these activated cells secrete chemicals that activate ___________ and increase ________ ________ maturation.

T cells, macrophages, dentritic cell (DC)

T cells are more numerous in

paracortical areas of lymph nodes

APCs and lymphocytes are found

throughout the lymphatic system although different sub types are found in more specific regions

DC and B cells are more numerous in

the germinal centers of the lymph nodes

Germinal centers

specialized microstructure that forms in secondary lymphoid tissues, producing long-lived antibody secreting plasma cells and memory B cells, which can provide protection against reinfection

Macrophages tend to remain fixed in

the lymphoid organs

Lymphocytes ___________ ____________ throughout the body

circulate continuously