Adaptive Immunity

Question 1

MHC class II molecules are only present on which type of cells?

Answer 1

APCs

Question 2

Which MHC class presents antigens from outside the cell? which one presents intracellular?

Answer 2

MHC I presents intracellular (CD8)

MHC II presents from outside (CD4)

Question 3

goals of lymphopoiesis

Answer 3

generate a diverse set of B and T lymphocytes

eliminate lymphocytes with self-reactive receptors

Question 4

where do B cells mature?

Answer 4

Bone marrow and spleen

(begins in bone marrow)

Question 5

Does a macrophage need a helper T cell to get activated and then destroy what it has swallowed?

Answer 5

I believe so (adaptive slide 9)

Question 6

What are the two divisions of the adaptive immune system?

Answer 6

humoral (antibodies) and cell-mediated (T and B)

Question 7

Positive vs negative selection in T cells:

Answer 7

Positive selection: refers to maturing only functional cells that can respond to the presentation of antigen on MHC

negative selection: refers to causing apoptosis in cells that are self-reactive (self meaning host proteins)

Question 8

What is the T cell referred to as once it matures but before it meet san antigen?

Answer 8

Naive

upon exposure, T cells undergo clonal selection so only those with highest affinity for given antigen proliferate

(T cells are born with CD4 and CD8 but eventually only one will stay)

Question 9

3 T cell types:

Answer 9

helper, cytotoxic, suppressor

Question 10

what are the chemicals called that get secreted by CD4 cells?

Answer 10

Lymphokines (recruit other immune cells and increase their activity)

ex. interleukins (main group of cytokines)

(cytokines main groups: interleukins and interferons)

Question 11

Which types of infections are helper T cells most effective against?

Answer 11

Bacterial, fungal, parasitic because helper T cells respond to antigens on MHC II complexes which are for extracellular pathogens (viruses are intra)

Question 12

Which types of infections are helper T cells most effective against?

Answer 12

Bacterial, fungal, parasitic because helper T cells respond to antigens on MHC II complexes which are for extracellular pathogens (viruses are intra)

Question 13

What do suppressor T cells do?

Answer 13

help to tone down immune response once infection has been adequately contained

also turn off self-reactive lymphocytes to prevent autoimmune diseases (called self-tolerance)

Question 14

What happens when immunoglobulins (antibodies) are secreted into body fluids rather than present on a cell surface?

Answer 14

1. Once bound to a specific antigen, they may attract other leukocytes to phagocytize those antigens immediately (OPSONIZATION aka more susceptible to phagocytosis)
2. May cause pathogens to clump together or agglutinate, forming large insoluble complexes that can be phagocytized
3. Can block the ability of a pathogen to invade tissues (neutralizing the pathogen)
4. Lysis of pathogen by complement activation
5. Precipitation into tissues

Question 15

response when antibody is on cell surface?

Answer 15

binding–> activation–> proliferation and formation of plasma + memory cells

(binding of an antigen to surface of mast cell causes degranulation, allowing the release of histamine and causing an inflammatory allergic reaction)

Question 16

Clonal selection with B cells:

Answer 16

B cells that can bind the invading antigen with high affinity survive and proliferate, generating specificity

Question 17

Constant region of antibodies:

Answer 17

The base of the Y is a region that cells such as NK cells, macrophages, monocytes, and eosinophils have receptors for, and that can initiate the complement cascade

Antibody molecules are like a fork in a meatball so antibodies don’t escape

(note: each b cell makes only one type of antibody but we have so many b cells that our immune system can recognize many antigens)

Question 18

Types of antibodies:

Answer 18

IgG: “really important for bacterial infections”
-65-75%
-made by plasma cells
-predominant antibody made after rechallenge of antigen aka secondary response
-bind macrophage and neutrophil receptors and activate compliment
-deficiency can lead to bacterial infections
-have you had this before in the past?

IgM: First to appear in primary immune response
-initial antibody type made by neonates
-Major antigen receptor on surface of mature B cells
-important component of immune complexes in autoimmune diseases
-pentamer
-are you sick now?

IgD: found in minute amounts
-together with IgM is major receptor for antigen on naive B cell surface

IgE: present in very low concentrations
-arms mast cells and basophils via Fc region
-results in release of mediators of immediate hypersensitivity (allergic) response

IgA:7-15%
-predominant class in secretions (tears, saliva, nasal, sweat, GI, human milk)
-dimer (4 sites)
-fixes complement via alternate pathway and has potent antiviral activity

Question 19

Which two antibody classes are very specific to killing and therefore are the only ones activating the complement cascade?

Answer 19

IgG, IgM

summary of antibody classes image on desktop

Question 20

What do naive cells do with their free time?

Answer 20

Wait in lymph nodes for their specific antigen to come along

Question 21

Primary response of B cells:

Answer 21

exposure–> proliferate (into plasma and memory B)

B cells wait in lymph nodes (can live forever, plasma cells die)

initial activation (primary response) takes 7-10 days

Question 22

Memory B cells:

Answer 22

just produce IgG

live up to 10 years in lymph node (not forever????)

differentiate into IgG secreting plasma cells when reactivated

response limited to peptide antigens, not lipid or carb

Question 23

What do cytokines do? What cells produce them?

Answer 23

Activate cells of innate and adaptive immunity

regulate be cell, macrophage, NK etc function

regulate inflammaton

CD4 (and CD8)

Question 24

In general, how do cytokines exert their effects?

Answer 24

by producing gene activation

Question 25

What do interferons do?

Answer 25

Inhibit viral replication

(know type I vs type II?)

Question 26

interleukins act between what?

Answer 26

leukocytes, duh

(leukocytes are all immune related cells)

Question 27

side note:

Answer 27

there are therapeutic cytokines and therapeutic blocking cytokines