Adaptive Immunity and Cell-Mediated Immune Responses

This flashcard set covers the properties and mechanisms of cell-mediated and antibody-mediated adaptive immunity, including T-cell and B-cell activation processes and APC functions.

When does adaptive immunity come into play according to the transcript?

It comes into play when innate immunity has failed to prevent an infection.

What are the four primary properties of adaptive immunity?

$1$.) Highly specific to a particular pathogen, $2$.) Memory (long-lasting protection), $3$.) Non-reactivity against self-antigen, and $4$.) Responses carried out by lymphocytes.

What are the two broad classes of adaptive immune responses?

Cell-mediated immune responses and antibody responses.

Which specific lymphocytes are responsible for carrying out adaptive immune responses?

$T$ cells and $B$ cells.

How is the interaction between a lymphocyte receptor and an antigen described?

They fit together like a lock and key (specific).

Where do $T$ cells originate and where do they mature?

They originate in the bone marrow but mature in the thymus.

What structure allows $T$ cells to interact with Antigen Presenting Cells (APCs)?

The $T$-cell Receptor ($TCR$).

When a naïve $T$ cell gets activated, what three types of cells can it differentiate into?

Effector $T$ cells (Helper $T$-cells and Cytotoxic $T$-cells) and Memory $T$ cells.

What is the specific role of Cytotoxic $T$-cells ($T_c$)?

They recognize the infected cells.

Which cell types are identified as Antigen Presenting Cells (APCs)?

Dendritic Cells, Macrophages, and $B$ cells.

Where are Dendritic Cells typically located?

In epithelial tissues (e.g., skin layers, mucosal tissues) and secondary lymphoid tissues/organs (lymph nodes, spleen).

What additional type of material can Macrophages process that Dendritic cells do not list?

Large particulate material such as dead cells.

What is the limitation regarding antigen presentation on a particular $MHC$ molecule?

The fragment of only $1$ type of microbe is presented on a particular $MHC$ molecule at any one time.

Which specific APC plays a major role in activating naïve helper $T$ cells?

Only Dendritic cells.

What are cytokines as defined in the transcript?

Chemical messengers secreted by cells to act on other cell types.

How do Cytotoxic $T$-cells kill infected cells?

By releasing perforins and granzymes.

What is another name for Antibody-mediated Immunity?

Humoral Immunity.

What are the two pathways for the activation of $B$ cells?

$T$ Cell-Independent and $T$ Cell-Dependent activation.

Describe the basic structure of an antibody.

A $Y$-shaped protein with $2$ arms.

In an antibody structure, what forms the antigen-binding site?

The variable regions.

What are the three possible organizational structures for antibodies mentioned?

Monomers (single $Y$-shaped molecule), dimers (paired), or pentamers (clusters of $5$ $Y$-shaped molecules).

What occurs during the process of Neutralization by antibodies?

Antibodies coat viruses and toxins completely, "neutralizing" them and removing the threat.

What is an immune complex?

A clump of antigens combined with antibodies that will be removed.

What characterizes $T$-cell Independent $B$ cell Activation?

It occurs when $B$-cell receptors ($BCRs$) interact directly with the antigen, inducing the $B$ cell to clone itself.

Into what cell type do clonal $B$ cells differentiate to produce antibodies?

Plasma cells.

What is a significant drawback of the $T$-cell Independent $B$ cell response?

It is short-lived and does not result in the production of memory $B$ cells.

What are the first two steps of $T$-cell Dependent $B$ cell Activation?

$1$.) Interaction between $BCRs$ and an antigen stimulates internalization, and $2$.) the antigen is processed and presented with $MHC\,II$.

During $T$-cell Dependent activation, what does the helper $T$-cell secrete to activate the $B$ cell?

Cytokines.

What is the function of memory $B$ cells produced during $T$-cell dependent activation?

To quickly respond to subsequent exposures to the same protein epitope.

What components of the innate immunity system are used for eliminating infected cells?

$NK$ cells, perforins, and granzymes.