L7- Adaptive immune responce

What lymphocytes are involved in adaptive immunity?

T cells

B cells

Features of adaptive immune system

• Diversity

• Specificity

• Memory

• Clonal expansion

Innate immune system recognises

Pattern recognition Receptors

Adaptive immune system recognises

specific invading microbes

Phenotypic structre of TCR

• Alpha chain + beta chain

• have constant and variable regions

Genetically what area of the TCR leads to high varibality

Complementarity-Determining Region 3

Gentically how is TCR diveristy made

• in germ line DNA have mutiple different V, D J segments

• have somatic recombination to come up with with different combination of VDK segments

• when joing up these different combinations can also add or remove nucelotides also helps increase diveristy

TCR signalling

• Once TCR binds to complementary peptide presented by MHC on APC

• the signal to divide doesnt come from TCR but from CD3

• CD3 is a TCR complex made up of odiffernet invarient chains that once activated by the bindng of TCR signall of T cell to divide

• most important chain is zelta chain in signalling

What are the 1st and 2nd signals needed for T cell activation

• first need TCR binding to peptide on MHC → not enough to actiavte T cell

• But in DC when TCR binds up resulated co stimulatory molecules CD80 and CD86 which are needed to activated T cell → this is the sencon signal

• need co stimulatory siganls to activate T cells

What happen if get no co stimulation

T cell enres state of anergy - inert doesnt do anything ust stays there doesnt die - need co sytimulation for activation and T cell to divide

What are the phases of T cell response

Charcteristics of T memoru cells

• have lower activation threshold

• More cells are responding

• Quicker response

• rapid expansion

What do niave T cells express on surface AND WHAT do effector// memory T cells express

• CD45RA

• CD27

• CD28

Memory / effector

• RO

Where do T cells normally exitsi

• they move throughout circulation into lymph nodes and around just looking

• less than 5% of lymphocytes are in blood at any one time

• memory T cells reside in tissue not in circulation

Migration of naive and effector T cells

What can T cells divide into

CD8 T cells

What are the different CD4 helper cells

• TH1

• TH4

• TH17

Th1

• Naive T cell → Th1

• secreted interferon - gamma

• activates macrophages to phagocytose microbes

• for bacteria

Th17

• Release IL-17 and IL-22

• IL-17 → inflammatory responce and neutraphil activation

• IL-22 → antimicrobrial peptides , incraese secreations e.g. mucus

• Th17 foudn in gut and skin

• for bacteria and fungi

Th2

• when have worms, helps with gut peristalsis

• IL-4, IL-5, IL-13

• IL-5 → esinophill activation

• IL-4 +13 → increase secretions, macrophages for tissue repair and peristalsis