This document summarizes cell-mediated immune responses by T lymphocytes. It discusses: 1) The phases of T cell responses including antigen recognition, costimulation, differentiation into effector cells, and signal attenuation. 2) How T cells recognize antigens through the T cell receptor complex and costimulatory molecules help activate T cells. 3) The roles and mechanisms of effector T cell subsets like Th1, Th2, and cytotoxic CD8+ T cells in fighting infection through secretion of cytokines and direct killing of infected cells. 4) How effector T cells migrate and are retained at sites of infection through adhesion molecules and homing receptors.

1. Cell-Mediated immune
responses
(Basic Immunology)
15/07/52

2. scope
-Phases of T Cell Responses
-Antigen Recognition and Costimulation
-Functional Responses of T Lymphocytes to
Antigens and Costimulation
-T Cell Signal Attenuation
-Migration and retention of effector T cells at
site of infection

3. Phases of T Cell Responses

4. Antigen Recognition and
Costimulation

5. TCR complex and its restriction

6. Components of TCR complex

7. Ag receptor of γδT cells
-TCR γ & δ chain consist of extracellular Ig-like
V & C regions, hydrophobic transmembrane
segment, short cytoplasmic tail เช่นเดียวกับ TCR
αβ
But not express CD4/CD8
-มักพบใน epithelial tissue (intraepithelial
lymphocyte)
-recognition : hypothesis
recognize Ag ที่พบบ่อยบน epithelial boundaries
between host & external environment

8. Structure of CD4 and CD8 coreptor

9. Costimulatory receptors of CD28 &
CD2 families &their ligand

10. Role of costimulators in T cell
activation
-2nd signal
-absense : fail to respond & die by apoptosis or
enter state of unresponsiveness (anergy)
-increase production of IL-2 & stabilize IL-2
mRNA
-promote survival of T cell

11. Role of costimulators in T cell
activation
1).CD28 bind to B7-1(CD80), B7-2(CD86) on
APC (dendritic cell, macrophage), B cell
2).ICOS(inducible costimulator) : activate
production of IL-10
3)CTLA-4(CD152) : self tolerance

13. Others accessory molecule on T cells
-CD44 acidic sulfated membrane glycoprotein :
mature T cell, thymocyte, B cell, macrophage,
granulocyte, erythrocyte, fiboblasts
-bind to hyaluronate : retention T cell in extravascular
tissue at infection site
-binding of activated & memory T cell to endothelium
at site of inflammation, in mucosal tissue

14. Others accessory molecule on T cells
(con.)
-CD40 ligand express บน activated CD4 T cell
bind to CD40 บน B cell, macrophage, dendritic
cell, endothelial cell
-Ligand for Fas (CD95)
-apoptosis
-important for eliminating T cell that are
repeated stimulated by Ag

15. Accessory molecules of T lymphocyte

16. Ligand-receptor pairs involved
in T cell activation

17. Regulation of integrin avidity

18. Clonal expansion (proliferation)

19. Signal transduction pathways
in T lymphocyte

20. Early tyrosine phosphorylation events
in T cell activation

21. Early tyrosine phosphorylation events
in T cell activation

22. T cell signaling downstream of
PLCγ1

24. Ras-Map kinase pathway in
T cell activation

25. Activation of transcription factors in T
cell

26. T cell signal attenuation
ทำำได้ 3 วิธี
1).activation inhibitory receptor of CD28
2).tyrosine-phospatases (SHP-1)
3).protein known as E3 ubiquitin ligases

27. T cell signal attenuation

28. Ubiquitin ligase Cbl-b in terminating T
cell responses

29. Differentiation of naïve T cell into
effector cell

31. Development of Th1 and Th2 subset

32. Cytokine signaling by the Jak-STAT
pathway

33. Characteristics of subsets of
CD4+ T cell

34. Effector function of Th1 cells

35. Effector function of Th2 cells

36. Activation of CD8+ T cells

37. Differentiation of CD8 T cell into
CTL
-ต้องกำร IL-12
-transcription factor :
T-bet & eomesodermin
-differentiated CTL secrete cytokine,
mostly IFN-γ, lymphotoxin, TNF
-cascade in differentiation same as
CD4

38. Effector of CD8+ T cell
steps in CTL-mediated lysis of target cell

39. Mechanisms of CTL-mediated lysis
of target cells

40. Action and functions of
macrophages in CMI

41. Migration and retention of effector
T cells at site of infection

42. Migration of naïve and effector
T lymphocytes

43. Recruitment of leukocyte
at infection site

44. T cell homing receptors and their
ligands

46. Thank you for your attention