Week 1 Adaptive Immunity and B cells

Question 1

Features of Adaptive Immunity
____: ____
____: ____
____: ____
____: ____
Antigen: ____

Answer 1

Features of Adaptive Immunity
Specificity: activated by and responds to a specific antigen

Versatility: ready to confront any antigen at anytime

Memory: “Remembers” previously encountered antigens and respond stronger and longer

Tolerance: Ignores normal tissues, responds to antigens

Antigen: part of a pathogen that can trigger an immune response.

Question 2

How These Features Are Achieved
Specificity & Versatility
____
____

B cell receptors bind to ____
T cell receptors bind to ____

Memory
____
→ ____: ____

Tolerance
____
Positive selection & negative selection:
T cells undergo positive and negative selection in the ____
B cells undergo positive and negative selection in the ____

Answer 2

How These Features Are Achieved
Specificity & Versatility
Both B and T cells have receptors that bind to specific shapes.
Different B and T cells have different receptors.

B cell receptors bind to free antigens in their native form
T cell receptors bind to both major histocompatibility
complex (MHC) and antigens displayed on the surface of other immune cells

Memory
Both B and T cells that have never encountered an antigen encounter an antigen
→ undergo clonal expansion: produce short-lived effector cells + long-lived memory cells
(e.g. vaccination)

Tolerance
Both B and T cells undergo positive and negative selection during their maturation.

Positive selection & negative selection: B/T cells that bind strongly to the body’s own protein will be deleted.

T cells undergo positive and negative selection in the thymus
B cells undergo positive and negative selection in the bone marrow

Question 3

Types of Adaptive Immunity
Active Immunity: ____
Naturally acquired: ____
Artificially acquired: ____

Passive Immunity: ____
Naturally acquired: ____
Artificially acquired: ____

Answer 3

Types of Adaptive Immunity
Active Immunity: Long-lasting immunity generated after exposure to a pathogen.
Naturally acquired:
Artificially acquired: Vaccination with antigen

Passive Immunity: Temporary immunity acquired via antibody transfer (e.g., mother to baby).
Naturally acquired:
Artificially acquired: Vaccination with antibodies

Question 4

B cells and Humoral (blood) Immunity
B cells make antibodies
Antibodies structure = ____ +____ (connected by ____)
Antibody regions = ____ (contains ____ )+ ____
____ region: ____
____region: ____

Answer 4

B cells make antibodies
Antibodies structure = 2 light chains + 2 long chains connected by disulfide bond

Antibody regions = Fab region (contains antigen binding site) + Fc region

Fab region: variable amino acid chains
Fc region: constant amino acid chains

Question 5

Activation of B Cells
1. ____
2. ____
3. ____

Answer 5

Antigen binds to a B cell receptor (that resembles the structure of the antibody), and is internalized, processed, and presented on MHC on the cell surface.

Helper T cells recognize both the antigen and MHC on B cells and secrete cytokines (e.g. interleukins)

The activated B cell divides into plasma cells (secrete antibodies) and memory B

Question 6

Antibodies
Functions
____ (function 1)
____ (function 2)
____ (function 3)
____ (function 4)
____ (function 5)
____ (function 6)

classes of antibodies
ig=____
____ → ____ →____/____/____
IgD= ____
IgM= ____
IgG= ____
IgA= ____
IgE= ____

Answer 6

Functions
1)Act as Opsonins for phagocytes chemotaxis
2)Antigen Clumping
Make them easier for phagocytes to engulf.
3)Inactivation of Bacterial Toxins (a type of antigen)
Bind to them and prevent them from binding to and harm the host cells.
4)Trigger Degranulation
Bind to pathogens and immune cells (NK cells, eosinophils, mast cell) and trigger them to release antibody-dependent cell-mediated cytotoxicity (ADCC) to kill the pathogens.
Mast cells can also release histamines and cytokines, contributing to inflammation.
5)Activate Complement proteins
6)Activate B Lymphocytes (when it’s in its transmembrane protein form)

Classes of antibodies (according to different Fc regions)
ig = immunoglobulin
IgD → IgM → IgG/IgE/IgA

IgD: B cell receptor, involved in B cell activation.
IgM: First antibody secreted; good for clumping antigens and activating complement.
IgG: Most common type of circulating antibody; Transferred across the placenta from mother to baby.
IgA: Protects epithelial surfaces; found in breast milk.
IgE: involved in causing inflammation (bind to mast cell/basophils), Involved in allergic reactions, parasite infections (bind to eosinophils).