chapter 15,

exam 3

Adaptive immunity

is protection from microbes that we acquire overtime through out exposure

• includes cell-mediated immunity (CMI) and humoral immunity (HI)

CMI deals w self cells- that are infected.

T-cells (thymus)

• Hi deals w microbe/toxin elimination from the blood

  • B cells (bone marrow) and antibodies

immature lymphocytes

Lacks antigen specific receptors

Naive lymphocytes

has not been activated by an antigen

activated lymphocytes

bound by its specific antigen (can proliferate)

Effector lymphocytes

Descendants of activated cells capable of carrying out a specific function

memory lymphocytes

long lived descendants that respond to a previously encountered antigen

ANTIGENS

• Antigens are molecules that elicit an immune response. can be pretty much anything (protein, lipid,sugars,etc)

• Antigens are often large molecules that contain epitopes which are distinct regions recognized

• Most antigens require a Tcell (t-dependent antigens) but some molecules like LPS are T- independent

B/T-cell Receptors

• All T cells have a T cell receptor (TCR) that binds antigens displayed on the surface of antigen-presenting cells (ie macrophages,dendritic cells)

• All B cells have a B cell receptor (BCR) that binds free floating antigen in our body fluids

Primary response

The first time a lymphocyte encounters a particular antigen

Secondary responde

• When a lymphocyte encounters the same antigen an additional time

  • secondary response are usually more robust and quicker than primary response

CMI (cell- mediated immunity)

• Naive T cells (not yet activated by antigen) encounter by antigen presented by a dendritic cell

  • If a DC has a costimulatory molecule and the T cell binds both the antigen and the costimulatory molecule, than the T cell can become activated.

• Active T cells proliferate and undergo differentiation to form Cytotoxic, Helper, or REGulatory cells,

  • Tc Cells (CD8+)

    • searches for cells that are infected to kill them

  • T H cells (CD4+)

    • produced cytokines that activate Macrophages and B cells

  • Tregs

    • stops an immune réponse

HI (Humoral Immunity)

• Different from CMI

• Naive B cells bind floating antigens and display them on their cell surface

• If a T H cells binds the B cells, then it will activate it.

  • T-Helper

• Activated B cells proliferate and differentiate into plasma or memory cells.

  • plasma cells

  • produced antibodies

Antibodies

• Y-shaped protein designed to recognize a specific antigen

  • the fab region binds antigen

  • the Fc region is bound by macrophage or other components of the immune system

• serves as a molecular flag indicating something ‘bad’ is here

Neutralization

prevents toxins.vriuses attachment to host cells

opsonization

helps phagocytic cells bind microbes

complementation

activates the classical pathway of complementation

immobilization

prevents microbes from moving or adhering to cells

Cross-linking

Can link microbes together forming a mass

Antibody dependent cellular cytotoxicity

helps natural killer cells destroy infected cells.

imprecise joining

• DNA coding for the B cell receptor can be inserted, swapped, or deleted during to create tons of different receptor sequence.

Clonal Expansion

• Rapid proliferation and multiplication of genetically identical cells from a single parent

  • allows the immune system to produce large numbers of specific T cells or B cells

T cell response

Antigens are presented on host cells by MHC molecules

• 2 different classes

MHC Class I

• only recognized by cytoxic T cells

• found on all cells in body

MHC Class II

• only recognized by helper T cells

• Found only on the surface of antigen presenting cells

The general rule to remember is the rule of 8. if u multiple the MHC class number the CD co-receptor number of the T cell, the answer must always equal 8

T cell activation

Dendrtic cells are like security cameras, keeping watch

T cell Response

All nucleated cells present MHC 1 molecules, with antigens that communicate what us going on inside the cell

Only B cells, Macrophages, and dendritic cells present MHC 2 molecules, with antigens from outside the body

Tc Cell response

C= cytotoxic because it kills the self care

T H cell response

H=helper, because it helps innate an immune response

B cell response

• B cells bind antigens present in body fluids ( Not on the self cells like the T cell response)

• The B cell receptor is shaped and functions like an antibody

B cell Activation

• Once activated, B cells differentiate into plasma cells and memory B cells

• Plasma cells are antibody factories

• Memory B cell sticks around long term for a more rapid secondary response to the same antigen

Antibodies

• Antibodies come in Different types called classes

• IgM—first antibody produced during primary response

• IgG—most abundant class of serum antibodies (many serum anti body tests are looking for IgG levels)

• IgA—most abundant antibody ( not much in serum — mostly secreted and lines the mucosal membranes)

• IgD—poorly understood

• IgE—bound to basophilic and mast cells (important for histamine response AKA allergies

• Class switching promotes antibody production of different classes)

• Occurs due to loss of DNA

  • only the first type gets produced in the sequence.

• immune responses rely on antibodies for memory

• memory lymphocytes are fine tuned for a specific antigen

  • can rapidly respond

  • respond more robustly

NK Cells

• Natural killer cells lack the antigen specific receptors

• recognize cells covered in antibodies or that lack MHC ( remember — all cells should display MHC class !)

• Induce apoptosis

Tolerance

• CMI and HI are powerful and have the ability to damage our own body

• Central tolerance — Takes place as lymphocytes mature elimination lymphocytes that recognize self antigens

  • destroy T- cells that recognize “self”

Lymphatic System

• Collection of organs and tissue that brings antigens into contact with T and B cells

• Lymph is similar to blood plasma

• primary lymphoid organs are where lymphoid develop

  • B cells = bone marrow

  • T cells = thymus

• Mature lymphocytes then migrate to secondary lymphoid organs to become wait for antigens and possible activation

  • lymph nodes

  • tonsils

  • spleen