GI tract and systemic immunity

Question 1

Type 1 Helper T cells, Th1

Answer 1

Recognize antigen and make a lymphokine that attracts thousands of macrophages, the heavy-duty phagocytes, to the area where antigen has been recognized.

Makes IFNγ, which attracts and activates M1 macrophages; and IL-2, which helps CTL get activated when they recognize antigen.

Question 2

Th17 Helper T cells, Th17

Answer 2

more powerful than Th1

Important in resistance to some tough organisms like Listeria, and to Candida.

Implicated in some serious forms of autoimmunity, usually along with Th1.

Make IL-17

Question 3

What pushes differentiation into Th17

Answer 3

Dendritic cells making IL-23

a new monoclonal antibody (tildrakizumab) specific for IL-23 is, in Phase 2 studies, remarkable effective in psoriasis. IBD will be next, as IL-23 is considered a central cytokine in Crohn Disease and possibly also ulcerative colitis.

Question 4

Type 2 Helper T cells, Th2

Answer 4

Stimulate macrophages to become M2 ‘alternatively activated,’ able to function in walling-off pathogens and promoting healing, a process that usually takes place after the pathogen-killing Th1 response.

Important in parasite immunity if the Th1’s M1 macrophages can’t kill the invader.

Make IL-4 which attracts not only macrophages but also eosinophils.

Question 5

Follicular Helper T cells, Tfh

Answer 5

Stimulated by antigen and migrate from T cell areas of lymph nodes into the B cell follicles, where they help B cells get activated and make the IgM, IgG, IgE and IgA antibody subclasses

Question 6

Regulatory T cells, Treg

Answer 6

Make cytokines (IL-10, TGFβ) that suppress the activation and function of Th1, Th17, and Th2 cells, so they keep the immune response in check.

Part of the Th family

Question 7

Cytotoxic or killer T cells, CTL

Answer 7

Destroy any body cell they identify as bearing a foreign or abnormal antigen on its surface, presented on Class I MHC.

Can also make IFNγ which attracts macrophages to eat the cells in which they induce apoptosis.

Question 8

CD4

Answer 8

A molecular marker found on Th1, Th2, Th17, Tfh, and Treg

increases their affinity for antigen, helps get them activated, and also serves us as a convenient tag for their identification

all look for antigen on MHC class II

Question 9

CD8

Answer 9

Marker on CTL

look for antigen on MHC Class I, on all nucleated cells