Immunology Exam 1 - Immune Cell Diversity and Adaptive Immune System

What are the key cells of the adaptive immune system?

B Cells and T Cells

What are the only lymphocytes with antigens-specific receptors?

B and T cells are the only cells with antigen-specific receptors; B cells have BCR receptors and T cell have TCR receptors

What are the functions of BCR and TCR receptors?

BCR and TCR receptors have extreme specificity when it comes to binding with antigens.

How can lymphocytes of similar type be differentiated from each other?

Lymphocytes contain different clusters of differentiation, which are cell molecules attached to the surface of the lymphocyte. They are designated by CD, followed by their classification number.

Where do B cells and T cells develop?

B and T cells develop from a common precursor of bone marrow origin. The specific sites where they begin to develop is called the primary lymphoid organs or primary lymphoid tissues.

Where is the site of T cell development?

Thymus (in between lungs)

How does the site of B cell development change depending on the species?

In birds, the site of B cell development is the bursa of Fabricius. In ruminants, the site of B cell development is in the ileal Peyer's patches (wall of small intestine). For most mammals, however, the site of B cell development is still in the bone marrow.

All primary lymphoid organs undergo involution (shrinking of organs due to old age or when inactive) except for which lymphoid organ?

Bone marrow

What are examples of secondary lymphoid tissues?

Lymph nodes, spleen and mucosa-associated lymphoid tissue

In what areas do B cells and T cells circulate in the blood?

Blood, secondary tissues, and lymph

What happens at the site of secondary lymphoid tissues?

T and B cells meet their specific antigens and further develop into effector cells.

Which secondary lymphoid tissue responds to antigens originated from the tissue?

Draining lymph nodes

Which secondary lymphoid tissue responds ton antigens that are delivered to the blood?

The blood

Which secondary lymphoid tissue responds to antigens originating at the mucosal sites?

mucosa-associated lymphoid tissue

Where does clonal selection and clonal expansion take place?

Secondary lymphoid organs

Thymus

-Located at the anterior mediastinum, composed of lobules, each with a cortex and medulla

-Medulla contains mature thymocytes, cortex contains immature thymocytes

-No afferent lymphatics

-Thymus undergoes evolution after puberty

-Epithelial cells and dendritic cells, filled by immature T lymphocytes and macrophages

Lymph Nodes

Composed of cortex, paracortex and medulla. Inverse structures in some mammals, including pigs, elephants and dolphins.

-The cortex contains follicles. Primary follicles consist of some B cells

-In secondary follicles with a germinal center, B cells proliferate and differentiate, which allows antigenic stimulation to occur

-Paracortex contains most T cells and dendritic cells. High endothelial venules are present in the paracortex

-Medulla consists of cords filled by plasma cells and macrophages

Spleen

-No afferent lymphatics

-White pulp consists of follicles from the periarteriolar lymphoid sheath and separated from red pulp at marginal zone

-Blood-borne antigens trapped my macrophages in marginal zone and transported to white pulp

How are immunoglobulin genes presented?

There are presented in fragments called gene segments

What is a germline configuration?

A germline configuration is the arrangement of immunoglobin gene fragments that it must be in in order for cells to inherit it

Where is the only location where rearrangement of gene fragments takes place?

Primary lymphoid gland where B cells are being developed

Which genetic regions are encoded by a single gene segment?

The L(leader) region and the C region

Which gene segments encode the light chain?

one V and one J gene segments

Which gene segments encode the heavy gene?

one V, one D and one J gene segments

What is somatic recombination in the context of the primary lymphoid organs?

Gene segments are cut and joined by DNA recombination (V(D)J recombinase). Generates additional diversity.

Describe junctional diversity in the context of the primary lymphoid organs

Deoxynucleotidyl transferase (TdT) add several nucleotides during the end of recombination

How is gene arrangement tightly controlled in the developing B cells?

B cells only express one heavy chain and one light chain

What is allelic exclusion?

Rearrangement of immunoglobulin genes in one allele shuts down the rearrangement process of another allele. Ensures that B cells produce antibody molecules of single-antigen specificity

Which invariant proteins are associated with B cell receptors?

Ig alpha and Ig beta

What is the function of invariant proteins Ig alpha and Ig beta

They allow for surface expression of immunoglobulin and signal transduction when the B cell receptors bind to a specific antigen

How do some species, like the chicken, employ a mechanism for generating immunoglobulin diversity

Through gene conversion, VJ and VDJ genes combine randomly with pseudogenes also located in loci, since there are few VJ and VD and J genes in their immune system

What is the effect of somatic hypermutation and class switching on antibody structure and function?

In secondary lymphoid organs, point mutations that occur at a rapid rate led to increased affinity for specific antibodies. Class switching is the capability of B cells to switch isotypes and classes of antibodies while maintaining antigen specificity. VDJ segment recombines with a different Ch coding gene segment other than Cu. Somatic hypermutations and isotype switching occurs after the B cell is activated by its specific antigen in secondary lymphoid organs.