Immune Response: Initial Infection

Immune Response: Initial Infection

Pathogens (disease-causing bacteria or viruses or other organisms) invade your body

Antigens (proteins that can be recognized by antibodies)

Immune Response Step 1: Initial Recognition of Infection

Cell-Mediated Response Antibody-Mediated Response

Macrophage

B Cell # 146,883

B Cell# 34,599

MACROPHAGE are white blood cells that gobble up foreign invaders.

MHC Protein

B CELLS are white blood cells that produce antibodies. Each person can produce hundreds of millions of different B

Cells. Each type of B cell is genetically-unique and produces a unique antibody. Two B cells(out of hundreds of

millions) are shown here.

ANTIBODIES are Y-Shaped proteins. The ends of the arms of the Y have antigen-binding sites. Each different

type of antibody has a uniquely shaped antigen-binding site.

Immune Response Step 2: Phagocytosis of Pathogen


Macrophage

MACROPHAGE engulf (phagocytize) the pathogenic invader. After this, the macrophage kills

and breaks down the pathogen into pieces.

The B CELL that has an antibody that binds to antigen engulfs(phagocytizes) the antigen-antibody complex. After this, the B cell kills and

breaks down the pathogen into pieces.

B Cell # 146,883

Immune Response Step 3: Antigen-Presenting Cells


Antigen-Presenting

CellAntigen-Presenting

Cell

MACROPHAGE display parts of the pathogen alongside the MHC protein. At this point, the

macrophage is called an Antigen-Presenting Cell (or APC).

The B CELLdisplays parts of the pathogen alongside the MHC protein. At this point, this B cell is called an Antigen-

Presenting Cell (or APC).

Immune Response Step 4: Helper T Cell-APC Interaction


Antigen-Presenting


Cell

T Cell # 2,888,124

T Cell #492

HELPER T CELLS are another kind of white blood cell. There are hundreds of millions of different kinds of T Cells. Each is genetically

unique and each displays a unique form of the protein called T Cell Receptor protein. Shown

here are two of the hundreds of millions of different kinds of T Cells in a persons body.

Immune Response Step 5: Helper T Cell Stimulation


Antigen-Presenting


Cell

T Cell # 2,888,124

Binding of Helper T Cell to APC stimulates the APC to secrete Interleukin. Interleukin stimulates Helper T cells to rapidly reproduce. Since Helper

T Cell # 2,888,124 is locked on, it will be in an area of high Interleukin concentration. So among

all the Helper T Cells floating around the body, Helper T Cell # 2,888,124 will be the one to

reproduce rapidly and repeatedly.

Immune Response Step 5: Helper T Cell Proliferation


Antigen-Presenting


Cell

T Cell # 2,888,124

Huge numbers of T Cell # 2,888,124 are produced.

T Cell # 2,888,124

T Cell # 2,888,124T Cell # 2,888,124

T Cell # 2,888,124

T Cell # 2,888,124

T Cell # 2,888,124 T Cell # 2,888,124

Immune Response Step 6: Helper T Cell DifferentiationCell-Mediated Response Antibody-Mediated Response

Antigen-Presenting


Cell

T Cell # 2,888,124

Cytotoxic T Cells kill body cells infected by the pathogen.

MEMORY T Cell # 2,888,124

CYTOTOXIC T Cell # 2,888,124

HELPERT Cell # 2,888,124

CYTOTOXIC T Cell # 2,888,124CYTOTOXIC T Cell # 2,888,124

CYTOTOXIC T Cell # 2,888,124CYTOTOXIC T Cell # 2,888,124


MEMORY T Cell # 2,888,124MEMORY T Cell #

2,888,124MEMORY T Cell #

2,888,124

MEMORY T Cell # 2,888,124 HELPERT Cell #

2,888,124HELPERT Cell # 2,888,124



Memory T Cells are fairly inactive. They reproduce at a steady pace.

Helper T Cells interact with other white blood cells to propagate the immune response.

Immune Response Step 7: Helper B Cell StimulationCell-Mediated Response Antibody-Mediated Response

Antigen-Presenting


Cell

T Cell # 2,888,124





HE

LP

ER

T C

ell # 2,888,124




HELPER T CELL #2,888,124 binds to the antigen-presenting B cell (#146,883)

since this B cell displays the same antigen-MHC complex. This binding stimulates Helper T Cell to secrete

Cytokines. Cytokines stimulate B cells to rapidly reproduce. Since B cell

146,883 is locked on, it will be the one to rapidly reproduce. Thus, the B Cell

that produces the antibody that binds to the current infectious agent is the one

that proliferates.

Immune Response Step 8: Helper B Cell ProliferationCell-Mediated Response Antibody-Mediated Response

Antigen-Presenting


Cell

T Cell # 2,888,124





HE

LP

ER

T C

ell # 2,888,124




Many copies of B Cell 146,883 are produced.

B Cell # 146,883

B Cell # 146,883B Cell # 146,883

B Cell # 146,883

B Cell # 146,883

B Cell # 146,883

B Cell # 146,883

B Cell # 146,883B Cell # 146,883

Immune Response Step 9: Helper B Cell DifferentiationCell-Mediated Response Antibody-Mediated Response

Antigen-PresentingCell

HE

LP

ER

T C

ell # 2,888,124

Plasma B Cells produce and secrete large quantities of antibodies. This helps to fight the current infection.

Memory B Cell # 146,883

Plasma B Cell#146,883











Memory B Cells are fairly inactive. They reproduce at a steady rate and will be present if the body is ever re-infected

with the same pathogen.

Immune Response Step 10: Immunity

Memory B Cell # 146,883Memory B Cell

# 146,883





If the body is ever again infected with the same pathogen, then the particular Memory T Cells and Memory B Cells that specifically recognize and bind this pathogen are already present. So steps 1-5 and 7-8 won’t have to happen. This makes for a faster immune response upon

re-infection (so you don’t feel like you’re sick).


2,888,124


2,888,124MEMORY T Cell #

2,888,124





Human Immunodeficiency VirusCell-Mediated Response Antibody-Mediated Response

Antigen-Presenting


Cell

T Cell # 2,888,124





HE

LP

ER

T C

ell # 2,888,124




HIV infects Helper T Cells. When HIV infects a person’s body, that stimulates an immune response. This causes an

increase in Helper T Cells. But this increase in Helper T Cells is an

increase in hosts as far as HIV is concerned.

Documents

Immune Response: Initial Infection