CD4+ T Cell Subsets Flashcards
CD4+ Th cell functions
▪ Effector function mechanisms:
• Secretion of cytokines
Cell mediated immunity vs humoral immunity
CMI - activate phagocytes (Th1)- intracellular organisms
Humoral immunity- extracellular organisms
Cytokines involved in CMI (intracellular)
IL-12 and IFN- Y
From Naïve to Effector CD4+ T cell
Naïve T cells are stimulated by microbial antigen presented by dendritic cells in the lymph nodes and spleen
▪ Express adhesion molecule: L-selectin
▪ Express chemokine receptor CCR7 (selective migration into lymph node)
▪ Gives rise to effector cell
▪ Differentiated effector T cell
migrate to site of infection
Activated T cell - Il12
-Th1
-IFN-g
TNF-a
-chronic inflammation and CMI
Activated T cell - IL4
Th2 IL-4 IL-5 IL-10 Humoral immunity and allergies
Activated T cell - IL6,IL1 and TGF-b
Th17
IL-17,IL-21,IL22
Inflammation and fungal immunity
Activated TGF-b
Treg
TGF-b
IL-10
Tolerance , immune suppression , regulation
IL 6 and IL21
CXCR5
Tfh
IL21
B cell differentiation and autoimmunity
Th1 cells
Production of IFN-g: ▪ Stimulate phagocyte-mediated ingestion • Expression of lysosomal proteases • Synthesis of reactive oxygen species and nitric oxide (deals with organisms that escape the phagosome) ▪ Stimulate production of antibodies that promote phagocytosis (IgG) ▪ Stimulate expression of Class II MHC and B7 on APCs (amplify T cell response) ▪ Activated macrophages produce IL-12 • Drives CD4+ T cells to Th1 cells (amplification) ▪ Same reaction: delayed type hypersensitivity (DTH)
Resistance of microbes to cell-mediated immunity-intracellular bacteria
inhibit fusion of phagosomes with lysosomes
• Escape into cytosol
• Escape phagocyte killing
Resistance of microbes to cell-mediated immunity- viruses
-inhibit class I MHC-associated antigen presentation
-inhibitory cytokines or decoy soluble
cytokine receptors that neutralize cytokines (
-directly infect T-cells (HIV-CD4+ T cells)
Mycobacteria resistance
They survive within the phagosome
HSV,CMV,EBV resistance
The inhibition of antigen presentation
Pox virus resistance
Inhibition of effected cell activation : production of soluble cytokine receptors
Di George syndrome
• Born without thymus,
lack T cell component
• Can fight extracellular pathogens but have issues with intracellular pathogens (viruses, intracellular bacteria)
-catch 22
Th2 cells
- humoral mediated immunity
- IL-4 ,IL5
- IL4 and IL-13 leading to IL10 production by M2
Alternative macrophage activation (M2)
✓Synthesis of extracellular matrix proteins for repair ✓inhibit microbicidal activity of macrophages
(suppresses Th1 cell-mediated immunity)
-anti inflammatory
Th1 up
Autoimmune problem
Internal threat
Th1 down
Cancer (hepatitis,HIV,shingles ,TB )
Th2 up
Allergic reaction
Th2 down
Infection
Extracellular organisms
Mycobacterium - Th1 response
Tuberculoid leprosy
Mycobacterium leprae - defective Th1 or dominant Th2
Lepomatous leprosy
