8-9. Lymphoid organs and Lymphocytes

T/F: lymphocytes only recognize processed antigens

true

what are the major surface lymphoid tissues?

respiratory tract, intestine, salivary glands, urogenital system, mammary glands

lymphocytes originate from __________ stem cells

pluripotent

where are lymphocytes produced in the embryo and fetus?

yolk sac and liver

where are lymphocytes produced in the neonate and adult?

bone marrow

where do b cells develop?

bone marrow

where do T cells develop?

thymus

how do naive lymphocytes try to increase the change of encountering a mature antigen?

move from blood to secondary lymphoid organs and return

_________ lymphoid organs are the site of lymphocyte development. what organs does this include?

primary

thymus, bursa of fabricius, peyers patches, bone marrow

________ lymphoid organs are sites where lymphocytes respond to antigens. what organs does this include?

secondary

tonsils, spleen, lymph nodes, peyers patches, bone marrow

what mediates expansion of stem cells and pro-lymphocyte populations during the early stage of maturation?

growth factors

when do cells commit to B or T cell lineage?

during early maturation which also initiates antigen receptor formation

After cells commit they populate their respective primary lymphoid organs. in these general organs the acquisition of what occurs?

functional competence

T/F: When selection of lymphocytes occurs, lymphocytes can still no discern themselves from foreign antigens

false, they can

what are the initial responders to foreign antigens?

mature lymphocytes (but still naive!!)

what occurs when a foreign antigen is presented to a mature lymphocyte?

they develop into differentiated effector lymphocytes and an immune response neutralizes or removes the foreign antigen

what is VDJ recombination?

the process by which T cells and B cells randomly assemble different gene segments - known as variable (V), diversity (D) and joining (J) genes - in order to generate unique receptors (known as antigen receptors) that can collectively recognize many different types of molecule

what is the site of maturation of T lymphocytes?

thymus

where are T cells found in the thymus?

cortex

where are antigen presenting cells found in the thymus?

corticomedullary region and medulla

explain how the anatomic arrangement of the thymus maximizes antigen encounters.

naive t cells circulate from cortex to medulla to maximize exposure to antigens, if they do not encounter antigens they will remain in circulation until they do

There are two main steps in T cell selection. Explain positive selection

ensure T cells can recognize self MHC molecule with moderate affinity which is necessary for activation and development progression

There are two main steps in T cell selection. Explain negative selection

ensures that T-cells that bind to self antigens are eliminated

where is the site of maturation of B lymphocytes?

bone marrow, bursa, peyers patches

what is the overall function of secondary lymphoid organs?

lymphocytes recirculate through these organs which maximized encounters with antigens to differentiate or become memory lymphocytes

what is the site of immune response to antigens in the blood?

spleen

what is the site of immune response to antigens along mucous membranes?

MALT

MALT tissue utilizes specialized cells like M cells to sample antigens from the mucosal surface. where are these M cells found and what exactly due they do?

follicle-associated epithelium (FAE)

transport antigens across mucosal barrier into underlying lymph tisse to initiate immune response

how do M cell process antigens?

internalize antigens via endocytosis and then transport across cell via transocytosis and deliver them to APCs

what is MALT antigen uptake and processing crucial for?

mucosal immunity, maintaining immune homeostasis, activate T and B cells, producing antibodies

what is the purpose of the cutaneous immune system?

antigens that penetrated stratified squamous epithelium are recognized by langerhans cells which migrate it to lymph nodes and presents it to other immune cells

what governs lymphocyte recirculation?

adhesion molecules and chemokines

what is the classic migration route of lymphocytes? (hint: think about what mediates it)

in short after recirculation it goes back to the lymph node then is receptor ligand mediated soo it eventually goes to the correct tissue

where is the highest percentage of lymphocytes found?

in lymph nodes

what are the only cells that recognize and respond to specific antigens? how?

T and B lymphocytes

capable of recognizing and binding to specific antigenic epitope

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

immunophenotype

___ cell is often called the master regulator of the immune response

T

CD4 is a _____ T cell

helper

CD8 is a _______ T cell

cytotoxic

which MHC class is CD4 associated with?

2

which MHC class is CD8 associated with?

1

What do T helper 1 cells regulate?

cell mediated immunity

what do T helper 2 cells regulate?

antibody protection

what molecules regulate signal transduction?

cytokine receptors

antibody receptors

complement receptors

integrins

selectins

what is the essential enzyme that initiates T and B cell activation? how?

tyrosine kinase phosphorylation bridges antigen recognition and immune response