1. Glycopathophysiology of immunity and inflammation
4/25/05

2. Large O-linked Glycosaminoglycans and poly-lactosamine structures
Glycoprotein N-linked and O-linked oligosaccharides
Glycolipid oligosaccharides

3. General Principles
Cell-surface glycans participate in all arms of the immune system
Glycan recognition is an integral component of innate (antibody-independent) immunity
Specific glycan structures modify humeral immune (antibody-dependent) responses
Differentiation of immune cell types requires appropriate glycan expression
Cell-cell interactions that lead to immune cell activation are modulated by carbohydrate

4. Today’s topics
Thymic selection of self vs. non-self
Innate immunity
Generation and function of the immune synapse
Carbohydrate-dependent antibody structure
Regulation of antibody production and B-cell responsiveness by glycan

6. Self vs. non-self selection
What does restricted mean? MHC I, MHC II, Cd1d?

7. Core-2 synthesis generates ligands for Galectins

8. Galectin binding induces apoptotic signals

9. C2GlcNAcT activity in relation to thymic selection
C2GlcNAcT expression by naïve T-cells in the thymic cortex increases with residence time and decreases as the differentiating T-cell migrates to the medulla
Strong TCR activation by self-bound MHC results in retention of the naïve T-cell in the cortex and maintenance of C2GlcNAcT activity (negative selection)
Weak TCR activation results in migration of the T-cell to the thymic medulla and down-regulation of C2GlcNAcT activity (positive selection)
C2GlcNAcT activity generates substrates for Galectin binding, leading to apoptosis of cortical T-cells

11. Tissue surveillance leads to the activation of T-cells and the
initiation of innate immune responses

12. Professional antigen presenting cells sit at the interface
between innate and adaptive responses

13. Innate immunity first then discuss antigen presentation

14. Innate immune responses detect the presence of pathogen, or
non-self molecular patterns--frequently these are glycans
Caroff, M., 2002

15. Caroff, M., 2002

16. Caroff, M., 2002

17. Takeda, K., 2003

18. Activation of dendritic cells by various TLR ligands produces
subsets of cytokines that activate adaptive responses
Iwasaki, A., 2004

19. Antigen presentation and the adaptive immune response

20. After Varki, A.

21. How is antigen presented?

22. Glycans are essential for peptide loading onto MHC-I
Rudd, P., 2001

24. The immunological synapse is the communication point for
activation of specific T-cells
Red/brown = cell adhesion molecules, integrins, Ig-CAM
Green/yellow = TCR, MHC I/II
White = outlines of T-cell on an APC
Dustin, M., 2000

25. Dustin, M., 2000

26. The synapse must accommodate glycans
Rudd, P., 2001

27. Galectins may organize components of the synapse, providing
a regulatory matrix that modulates signaling levels--GlcNAcTV
KO has overactive signaling
Lowe, J., 2001

28. T-cell activation leads to altered O-linked glycan expression
Tsuboi, S., 2001

29. Altered glycosylation of CD43 (leukosialin) modulates the synapse
Tsuboi, S., 2001

30. T-cell activation modulates B-cell responses

31. Th1--IFNg, IL12, microbial responses, auto-immunity
Th2--IL4, 5, 6, 9, 10, 13, parasite responses, asthma, allergy

32. IgG1 glycans are essential for antibody function
Rudd, P., 2001

33. Under galactosylated IgG1 is recognized by MBP, leading to
complement activation--mechanism of pathology in RA and SLE?
Rudd, P., 2001

34. Sialic acid-recognizing Ig-superfamily lectins)
Human Siglecs
Sialic acid-recognizing Ig-superfamily lectins)
Arg97
Trp2
Trp106
Neu5Ac G 4
MAG
Glia 3
CD33
Myeloid
Precursors
Monocytes
Macrophages A F
10x 1
Sialoadhesin
Macrophage
Subset
V-set domain
C2-set domain 2
CD22
B cells
?Basophils
After Varki, A.

35. Three Possible Models for Functions of CD22-Sialic Acid Interactions
Collins, B., 2002

36. Sialic acid-recognizing Ig-superfamily lectins)
Human Siglecs
Sialic acid-recognizing Ig-superfamily lectins)
Human Siglecs
(Sialic acid-binding Ig-superfamily lectins)
ITIM
ITAM
Putative Tyr-based motif
V-set domain
C2-set domain
10x 1
Sialoadhesin
Macrophage
Subset 2
CD22
B cells
?Basophils 5
Neutrophils
Monocytes 6
OBBP-1
Placenta
B-cells 11
Macro-
Phage 10
Eosinophils 9
Granulocytes
T cell
subset 8
SAF-2 7
AIRM-1
NK cells
T cell subset
CD33(Siglec-3)-related Siglecs 4
MAG
Glia 3
CD33
Myeloid
Precursors
Monocytes
Macrophages

37. B-cells and glycans
Subsets of antibodies require appropriate glycosylation for function
B-cell activation is modulated by carbohydrate-lectin interactions

38. General Principles
Cell-surface glycans participate in all arms of the immune system, where they:
Mediate or regulate cell adhesion
Modulate cell signaling events
By regulating signaling and adhesion, progenitor cells are driven toward specific differentiation/activation by glycan expression
Immunoglobulins, especially, require specific N-linked glycans for stability and activity

43. xx

44. xx

47. General Principles 1 2 3 4 5 6