Lymphoid Organs & Lymphocytes

Where do lymphocytes originate?

pluripotent stem cells in the yolk sac & liver (embryo) and the bone marrow (adult)

If they develop in the bone marrow they become:

B cells

IF they develop in the thymus they become:

T cells

Describe the general movement of naive lymphocytes.

constantly move from blood to 2° lymphoid organs and return which increases the chance of encountering a mature antigen presenting cell

List the primary lymphoid organs (4)

• thymus

• bursa of fabricius

• peyer’s patches

• bone marrow

List the secondary lymphoid organs.

• tonsils

• spleen

• lymph nodes

• peyer’s patches

• bone marrow

The ______ lymphoid organs are he site of lymphocyte development.

Primary

The ______ lymphoid organs are he sites where lymphocytes respond to antigen

secondary

VDJ recombination

Antigen receptor initiation and formation that creates diversity in the receptors

Where does VDJ recombination occur?

primary lymphoid organs

The cortex of the thymus is dark purple due to a rich population of:

T cells

The medulla of the thymus is light pink due to the rich population of:

antigen presenting cells

What happens if an antigen is encountered as the lymphocytes circulates from the cortex to the medulla of the thymus?

naive T cell will develop into an effector cell

What happens if an antigen is not encountered as the lymphocytes circulate from the cortex o the medulla of the thymus?

T cells will enter efferent lymphatics and circulation until and antigen is encountered

Positive T cell selection

a process that ensures developing T cells can interact with self-MHC molecules; T cells that bind to self-MHC molecules with moderate affinity receive survival signals, allowing them to progress further in development

Negative T cell selection

T cells that strongly recognize self-antigens presented on MHC molecules receive signals that trigger apoptosis

In secondary lymphoid organs, they lymphocytes that recognize antigen whill interact, proliferate, and differentiate into:

memory lymphocytes

The follicles in lymph nodes are made up of _____ and surrounded by ______

B cells; T cells

The spleen is the site of immune response to antigens in the _____

blood

Where does immune response to antigens in he mucous membrane occur?

Mucosa associated lymphoid tissue (MALT)

What do M cells do?

sample antigens from mucosal surfaces and transport them int the underlying lymphoid tissue for the immune response

Where are M cells found?

follicle associated epithelium (FAE)

What antibody gets made at MALT from transportation of M cells?

IgA

CUtaenous lymphoid immune system

Process through which immune system responds to antigens penetrating stratified squamous epithelium

What cells work in the cutaneous immune system to engulf pathogens?

Laangerhans cells

Where do laangerhans cells go?

Lymph nodes

True or False: Lymphocyte recirculation is governed by adhesion molecules and chemokines

TRUE

True or False: The migraion route of lymphcytes is random.

FALSE - ligand mediated o ensure they are in the right tissue for the right response

What are the typs of lymphocytes?

• B lymphocytes

• T lymphocytes

  • Cyotoxic T

  • Helper T

• NK cells

• Regulatory lymphocytes

_____ and ______ lymphocytes are the only cells that recognize and respond specifically to antigens

B and T

True or False: There are only a small amount of cells dedicated to each antigen epitope BUT they can multiply when needed for an immune responsew

TRUE

Immunophenotype

process that identifies cells based on the types of antigens or markers on the surface of the cell

What is the master regulator of the immune system?

T cells

What do B cells do?

secrete antibodies

WHat kind of antigen receptors do B cells have?

surface immunoglobulins

WHat do T helper 1 cells d?

upregulate cell mediated immunity

What do T helper 2 cells do?

upregulate antibody production

What is the fundamental step in T and B cell activation?

tyrosine phosporylation