Lymphocyte activation, homing, and trafficking

Question 1

How are foreign antigens ultimately presented to the T cells?

Answer 1

1.Lymphatic capillaries can pick up interstitial fluid and carry it into the lymph nodes

2.Dendritic cells internalize antigens, after grabbing them from the tissue, and bring it to the regional lymph nodes where they present it to the T cells (when engulfed, the antigens are BROKEN down into small peptides that are then presented to the TH and TC cells that are SPECIFIC TO THAT PEPTIDE THROUGH Mac I AND II)- TCR’s will then recognize the antigen presented

3. OR B cells engulf FREE antigens and present them to the TH cells

Question 2

after MHC I and II activate Tc and Th cells accordingly, what job will ETh, ETfh, ETc, and Memory T cells will carry out during infection?

Answer 2

-proliferation of effector and memory T cells will take place

Effector T Helper cells: will migrate to infected areas and secrete cytokine for cell distinction, and these cytokines are potent activators of macrophagesand help them to become more efficient killers of the pathogens.

Effector T follicular help cells: will migrate to the germinal centers , were they will provide cytokines to activate and help select B cells that have high affinity ( proliferation, differentiation,
class switching, antibody affinity maturation and memory B cells formation)

Effector T cytotoxic cells: will migrate to inflamed areas and KILL THE INFECTED HOST CELLS by secreting PERFORIN AND GRANZYMES (granzymes induce apoptosis)

Memory T cells: will monitor SLO (AND NON- MALT organs) for post- antigenic exposure EXCEPT MALT( NOT MALT!)

memory B cells will only monitor SLO

**EFFECTOR T c and h CELLS WILL DIE BY APOPTOSIS WHEN ANTIGEN IS ELIMINATED

Question 3

What does B cell activation and differintiation look like?

Answer 3

a. The free-antigen is brought to the lymph node (Figure 1). Those B cells that are specific to the antigen (naïve B cells at first time antigen exposure) bind to it by their surface-expressed antibody molecules or BCRs (IgM and IgD
antigen receptors for naïve B cells).

b. The BCR-bound antigen is endocytosed and processed (chopped up into small pieces i.e. small peptides) by the B cells.

c. Small peptides of the antigen are loaded onto the class II major histocompatibility complex (MHC II) molecules inside the B cell and then trafficked to the cell surface for presentation to a peptide-specific Th cell.

Although BCRs can recognize all types of antigens (such as proteins, carbohydrates and lipids), they CAN ONLY PRESENT PROCESSED PROTEIN PEPTIDES OF ANITGENS TO T CELLS

Question 4

Who are the APCs? and which are the most successful?

Answer 4

-B cells
-macrophages
-Dendritic cells

Dendritic cells are more successful because they have more MHC I and MHC 2, as well as can also present protein peptides to effector T cells, and not just naive cells

Question 5

Fill out this table

Question 6

True or false: the cell response develops in the draininng lymphoid organs and the effector th cells migrate to the inflamed skin and the non-inflamed liver where they produce cytokines

Answer 6

FALSE- only migrate to inflamed areas

Question 7

Th cell response develops in the draining lymph nodes, and the memory th cells can migrate to the inflamed skin and to the non-mucosal sites, such as the non-inflamed liver

Answer 7

TRUE- bc its T cells, B cells remain in lymphoid organ

Question 8

Long-lived serum antibody responses are due to long lived __________ in the _____________

Answer 8

PLASMA CELLS
BONE MARROW

Question 9

EFFECTOR b CELLS AND MEMORY B CELLS DO NOT LEAVE THE SLO!!!!!!

Question 10

true or false: B cell response develops in the draining lymph nodes, and some of the specific plasma B cells migrate into the inflamed skin where they produce antibodies, which contribute to eliminating the pathogen by phagocytes

Answer 10

FALSE

Question 11

true or false: B cell response develops in the draining LNs. some of the specific plasma cells migrate to the spleen where they produce antibodies. the antibodies via blood enter the skin and contribute to eliminating the pathogen by the phagocytes

Answer 11

TRUE

Question 12

pathogens or antigens that enter the body via parental routes (skin, blood, muscle) DO NOT induce immunity in the MUCOSAL SURFACE…. BUT mucosal surfaces can incur immunity in the parental routes

Question 13

effector Th and Tc cells only go to inflamed areas in SLO BUT in MALT, they will go to inflamed AND NON-inflamed areas of the mucous tissue

all other steps of MALT remain the same (but in mucous)

Question 14

Antigens are presented into MALT by transcytosis

The antigen is taken up by DENDRITIC CELLS which
process it for presentation to T cells.

The Th and Tc proliferate and differentiate
into effector and memory Th and Tc cells.

Antigens are also picked up by B cells, which present them to the Tfh cells to receive cytokine help. Activated B cells
proliferate and differentiate into memory and plasma cells.

Answer 14

Mainly secretory IgA molecules produced into the lumen where they can block entry of the pathogens.