IB 202 Adaptive Immunity: Response and Memory

What are the 2 mechanisms of the adaptive immune response?

1) humoral response- promoted by TH2 cells and involves production of antibodies and other proteins secreted into blood and lymph

2) cell-mediated response- promoted in TH1 cells and activates phagocytic cells and cytotoxic T cells (activated CD8+ cells), cell-to-cell contact

How are extracellular pathogens eliminated? Overview

-humoral response

-when B cell recognizes invader it’s activated by TH2 helper T-cells:

• activated B cell replicates and differentiates in plasma cell

• antibodies from plasma cells attach to extracellular bacteria, fungi, viruses, and other foreign material

4 Steps of Humoral Response Eliminating Extracellular Pathogens: Different Antibodies

1) Opsonization- coating of pathogen and destruction by phagocytes

2) Neutralization- blocking coated cells from interacting with host cells

3) Agglutination- clumping of antigens caused by antibodies

4) Co-stimulation of complement proteins- activating lethal group of proteins called complement system

How are intracellular pathogens eliminated?

-Cell-mediated response

-cytotoxic T cells

-I MHC proteins involved in cell-mediated response

3 Steps of Cell-Mediated Response Elimination Intracellular Pathogens

1) recognition- cytotoxic T cell recognizes and binds to infected cells

2) directed secretion- T-cell vesicles secrete proteins to form pores and other proteins that pass through pores into cytoplasm of infected cell

3) apoptosis- T cell leaves, infected cell fragments: phagocytic cell consumes fragment to eliminate intracellular pathogens

Immunological Memory

-activated B and T cells produce memory cells (not in primary immune response) but remain in spleen and lymph nodes waiting to respond

-secondary immune response if same antigen enters again

Immune Response Speed

-secondary adaptive immunity is faster with stronger response b/c same antigen enters a second time

Markers of Self and Non-Self

-discrimination of self and non-self-antigens achieved by negative and positive selection of T cells in thymus

-non-self cells can be pathogens or cells from another person

How to prevent strong immune responses in blood and organ transplants?

-prevent strong immune reactions

in organ transplant recipient:

• donor with similar MHC proteins

• treat recipient with drugs that suppress immune response

Blood Transfusions

-innate and adaptive immune systems can have deadly responses

-membrane glycoproteins A and B act as antigens if introduced into person with blood cells without that antigen

Multiple Sclerosis: Overview

-MS damages myeline on nerve fibers in CNS

4 Steps of MS

1)B cells recognize myelin and T cells launch immune attack

2) T and B cells release chemicals to attract other immune cells causing inflammation

3) B cells make antibodies to attack myelin and recruit help of other immune cells

4) T and B cells establish permanent residence in CNS to continue attack

What is the outcome of celiac disease?

Type 1 Diabetes and T cells

cytotoxic T cells attack insulin producing cells leading to high blood glucose

How is Type 1 Diabetes different from Type 2 involving different cells?

Alopecia and T cells

-autoreactive cytotoxic T cells recognize melanocyte-associate proteins

-increase in MHC I/II expression