A&P2 Specific Immune Response

What are the two main types of specific immune responses?

Cell-mediated immunity and antibody-mediated immunity.

In which organ do T cells mature?

The thymus.

In which location do B cells mature?

The bone marrow.

Which specific T cell type is the primary effector of cell-mediated immunity?

Cytotoxic T ($T_C$) cells.

Which specific cell type is the primary effector of antibody-mediated immunity?

Plasma cells (derived from B cells).

Which category of cells is required for T cells to recognize antigens?

Antigen-presenting cells (APCs).

Identify the four main types of Antigen-Presenting Cells (APCs).

Dendritic cells, macrophages, reticular cells, and B cells.

What is the primary function of Major Histocompatibility Complex (MHC) proteins?

They act as cell "identification tags" to label every cell as belonging to the individual.

MHC proteins are structurally unique for every individual except for _.

Identical twins.

What are Langerhans, (aka dendritic cells)?

Mobiles APCs of the skin, mucous membranes, and lymph organs

Which stationary APC is found in the stroma of lymphatic organs?

Reticular cell.

Macrophage is?

A large phagocytic cell that engulfs and digests cellular debris and pathogens (used to be monocyte in blood)

What is the antigen-presenting cells steps?

• APC encounters antigen

• Internalizes it by endocytosis

• Digests it into molecular fragments in lysosome

• Displays relevant fragments (epitopes) in the grooves of the MHC protein

Which organelle is responsible for digesting internalised antigens in an APC?

The lysosome.

Where on the MHC protein are processed antigen fragments (epitopes) displayed?

In the grooves of the MHC protein.

What occurs when a wandering T cell encounters an APC displaying a self-antigen?

The T cell disregards the cell.

What occurs when a wandering T cell encounters an APC displaying a nonself-antigen?

The T cell becomes activated, initiating an immune attack

What alerts the immune system to presence of foreign antigen?

APCs

What chemical messengers are required to coordinate the activities of various immune cell types?

Cytokines (such as interleukins).

MHC Class I proteins are found on which cell distribution?

All nucleated somatic cells.

MHC Class II proteins are primarily found on which cell type?

Antigen-presenting cells (APCs), activated T cells

Which T cell surface marker recognizes MHC Class I proteins?

The CD8 marker

Which T cell surface marker recognizes MHC Class II proteins?

The CD4 marker

CD8+ T cells differentiate into which functional cell type?

Cytotoxic T cells.

CD4+ T cells differentiate into which functional cell type?

Helper T cells.

What’s an HLA?

Human Leukocyte Antigen

What do HLA do?

HLA genes encode MHC proteins

What is the importance of HLA genes?

Distinguish each person as unique, important in transplant tissue matching

What does the immune system use to know what to attack as foreign?

HLA molecules (the basis of self vs. non-self)

What does MHC-I and MHC-II tell the cells?

MHC-I: proteins tell cytotoxic T cells to kill the infected cell before it can infect other cells

MHC-II: proteins tell helper T cells to start an immune response against the antigen

In cell-mediated immunity, what proteins are released by T_c cells to destroy target cells?

Perforin and granzymes.

Which cytokine secreted by T_H cells specifically stimulate T_c cells and activates macrophages?

Macrophage-activating factor (MAF).

What is the sequence for Cell-Mediated Immunity (helper T & Cytotoxic T cells)?

1. Virus invades cell (or cancer cell)

2. T_c cells are activated by antigens presented on the surfaces of infected cells, and they form a clone (copies of cell, mitosis)

3. When activated by a foreign antigen-MHC-II complex by an APC and by cytokines, a T_H cell divides and gives rise to a clone of T_H cells

4. T_H cells release cytokines that stimulate T_c cells and activate macrophages so that they phagocytose pathogens

5. T_c cells release perforin & granzyme that destroy infected cells by apoptosis

CD4+ Helper T cell do?

• Binds Ag-MHC-II

• Secretes MAF, interleukin & other cytokines

What does Macrophage-activating factors do?

Activate macrophages and inhibit them from wandering away from infection site

Chemotaxic does what?

Attract neutrophils, NK cells, and macrophages to infection site

What receptors recognize MHC-I and MHC-II antigens?

CD8+ Cytotoxic T cells recognize MHC-I antigens

CD4+ Helper T cells recognize MHC-II antigens

Interferon

Inhibit viral replication (spares neighbor cells not infected by virus) & recruits macrophages

What is tumor necrosis factor (TNF)?

Activates macrophages, kills cancer cells

What is the result of "Positive Selection" in the thymus?

Keeps T-cell that recognize MHC

What is the purpose of "Negative Selection" in the thymus?

It eliminates T cells that bind too tightly to self-antigens to prevent autoimmune disease.

In which specific part of the thymus is the immature T cell receptor (TCR) expressed?

The cortex.

What is the primary function of Regulatory Treg (alos cells?

They prevent autoimmunity.

In a B-cell immune response, which cell type interacts with the B cell to trigger its activation?

Activated Helper T ($T_H$) cell.

Once activated, B cells differentiate into which two cell types?

Plasma cells and memory B cells.

What is the specific term for an antibody molecule's tail fragment?

The $Fc$ fragment (Constant region).

Which part of the antibody molecule binds to the specific antigen?

The $Fab$ fragments (Variable region/arms).

The process where antibodies coat the surface of a pathogen to increase phagocytosis is called _.

Opsonization.

What is the specific term for the portion of an antigen that fits into the antibody's binding groove?

Epitope (or antigenic determinant).

Which class of immunoglobulin is the most abundant, making up $80\%$ of total antibodies?

$IgG$.

Which immunoglobulin class is found in breast milk and provides passive immunity to babies?

$IgA$.

Which immunoglobulin is the principal antibody synthesized during a primary immune response?

$IgM$.

Which class of antibody is primarily involved in allergic reactions and histamine release?

$IgE$.

What enables the massive diversity of different antibody structures?

Gene rearrangement/shuffling of the DNA sequence.

How long does it typically take for specific antibodies to appear in the blood after first exposure?

3 to 14 days.

Which immunoglobulin is the primary antibody produced during a secondary immune response?

$IgG$.

How does the latent period of a secondary immune response compare to a primary response?

The secondary response has a much shorter latent period.

A vaccination is an example of which type of immunity?

Active, artificially induced immunity.

The transfer of $IgA$ antibodies from mother to baby is which type of immunity?

Passive, naturally induced immunity.

Receiving a RhoGam injection or antivenin represents which type of immunity?

Passive, artificially induced immunity.

Which type of immunity (Active or Passive) results in the development of memory cells?

Active immunity.

Concept: Monoclonal Antibodies (mAbs)

Definition: Highly specific antibodies produced by a single clone of hybridoma cells, providing an unlimited supply.

How are hybridoma cells created for mAb production?

By fusing myeloma (cancer) cells with B lymphocytes from the spleen.

Which specific cells does HIV primarily attack and enter?

CD4+ Helper T cells.

Which two proteins on the Helper T cell surface are used by HIV for entry?

CD4 protein and CCR5 receptor.

Autoimmune diseases like Multiple Sclerosis (MS) are often caused by the failure of _.

Negative selection in the thymus.

In Type 1 Diabetes, the immune system destroys which specific cells in the pancreas?

$\beta$-cells (beta-cells).

What medication is used to prevent Rh incompatibility reactions in $Rh-$ pregnant women?

RhoGam.

In an allergic reaction, which cell type releases histamine after allergen-IgE binding?

Mast cells.

What biological basis is used to match donors and recipients for organ transplants?

MHC/HLA matching.

What does the acronym GVHD stand for in the context of bone marrow transplants?

Graft versus Host Disease.

In BMT, what is the beneficial effect of donor T cells attacking remaining tumor cells?

Graft versus Leukemia (GVL).

Which antibody class forms a pentamer structure with 10 antigen-binding sites?

$IgM$.

What happens to a T cell that fails "Exam 1" (does not recognize MHC)?

It undergoes apoptosis (R.I.P.).

Which cells provide a poor prognosis for cancer when found in the tumor mass?

Myeloid-derived suppressor cells (MDSC) and Regulatory T ($T_{Reg}$) cells.