Aging of the Immune System

1. Aging of the Immune System Dr. Hal Sternberg BioTime, Inc. Berkeley, CA

2. Evidence for Decline in Immune Function with Aging Aged Individuals have: 1) Increased incidence of INFECTIONS: For example: pneumonia, influenza, tuberculosis, meningitis, urinary tract infections 2) Increased incidence of AUTOIMMUNE DISEASE: For example: rheumatoid arthritis, lupus, hepatitis, thyroiditis (graves-hyper/hashimotos-hypo), multiple sclerosis (Predisposition toward these diseases is related to Human Leukocyte Antigens HLA genes)

3. Evidence for Decline in Immune Function with Aging Aged Individuals have: 3) Increased CANCER INCIDENCE: For Example: prostate, breast, lung, throat/neck/head, stomach/colon/bladder, skin, leukemia, pancreatic 4) TOLERANCE to organ transplants: Kidneys, skin, bone marrow, heart (valves), liver, pancreas, lungs

4. Function of Immune System is PROTECTION against: • Bacteria • Virus • Fungus/ multicellular parasites • Cancer • Toxins • ( 5,000 daltons--protein/lipid/CHO/nucleic acids)

5. Tissues and Organs Important for Immune Function • Cells derived from stem cells: liver, bone marrow • Cells are stored, multiply, interact, and mature in: thymus, spleen, lymph nodes, blood • Transport: lymphatic vessels • Accessory Organs • Appendix, tonsils, intestines

7. Cell Types • Lymphocytes: derived in bone marrow from stem cells 10^12 • A) T cells: stored & mature in thymus-migrate throughout the body • -Killer Cells • Perform lysis (infected cells) • Cell mediated immune response -Helper Cells Enhance T killer or B cell activity -Supressor Cells Reduce/suppress immune activity May help prevent auto immune disease

8. Lymphocytes (cont.) • B-Cells: stored and mature in spleen • secrete highly specific Ab to bind foreign substance (antigen: Ag), form Ab-Ag complex • responsible for humoral response • perform antigen processing and presentation • differentiate into plasma cells (large Ab secretion)

9. Neutrophils- found throughout body, in blood -phagocytosis of Ab-Ag CX Macrophages- throughout body, blood, lymphatics -phagocytose non-specifically (non Ab coated Ag) -phagocytose specifically Ab-Ag CX -have large number of lysosomes (degradative enzyme) -perform Ag processing and presentation -present Ag to T helper cell -secrete lymphokines/ cytokines to stimulate T helper cells and immune activity 4. Natural Killer Cells-in blood throughout body -destroy cancer cells -stimulated by interferons

10. Macrophage Bacteria Bacterial Infection

11. Complement Series of enzymes which are sequentially activated and result in lysis of cell membrane of infected cell at bacterium Permeablizes membrane leaky Complement binding and activation ~35 enzymes and factors involved in cascade

12. Viral Infection

14. 5 classes of Ig IgG: 150,000 m.w. most abundant in blood, cross placental barrier, fix complement, induce macrophage engulfment IgA: associated with mucus and secretory glands, respiratory tract, intestines, saliva, tears, milk variable size IgM: 900,000 m.w. 2nd most abundant , fix complement, induce macrophage engulfment, primary immune response

15. 5 Classes of Ig IgD: Low level in blood, surface receptor on B- cell IgE: Binds receptor on mast cells (basophils) secretes histamine, role in allergic reactions Increased histamine leads to vasodilation, which leads to increase blood vessel permeability. This induces lymphocyte immigration swelling and redness.

17. Thymus Involution Cortex Repertoire of lymphocytes shift with aging (membrane components shift)

18. Experimental Evidence for Age Related Decrease in Immune Function Sheep RBC (Antigen) 1st into human Dependent on T & B cell function

19. B-Cell Mitogenesis Strain dependent, mitogen dependent, etc. • Mitogen • Lipopolysac. • PHA In vitro

20. Table 15-2: Some Aging Related Effects on B-Cells • Decreased number of circulating and peripheral blood B cells • Alteration in B-cell repertoire (diversity) • Decreased generation of primary and secondary memory B cells • General decline in lymphoproliferative capacity

21. Table 15-14: Some Aging-Related Effects on T-cells • General decline in cell mediated immunological function • T-cell population is hyporesponsive • Decrease responsiveness in T-cell repertoire (i.e. diversity of CD8+ T-cells) • Decline in new T-cell production • Increase in proportion of memory and activated T-cells while naïve T-cells decrease • Diminished functional capacity of naïve T-cells (decreased proliferation, survival, and IL-2 production) • Senescent T-cells accumulate due to defects in apoptosis • Increased proportion of thymocytes with immature phenotype • Shift in lymphocyte population from T-cells to NK/T cells (cell expressing both T-cell receptor and NK cell receptors)

22. Table 15-13 Aging-Related Shifts in Antibodies • General decrease in humoral responsiveness: • Decline in high affinity protective antibody production • Increased auto-antibodies: • Organ specific and non-organ specific • antibodies directed to self • Increased serum levels of IgG (i.e. IgG1 and IgG3) and IgA; IgM levels remain unchanged

23. Table 15-16 Influence of Aging on Macrophages • and Granulocytes • General functional impairment of macrophages and granulocytes • GM-CSF is unable to activate granulocytes from elderly subjects (e.g.: superoxide production and cytotoxic abilities) • Polymorphonuclear neutrophils appear to possess higher levels of surface markers CD15 and CD11b and lesser vesicles containing CD69 which lead to the impairment observed to destroy a bacteria • In elderly subjects the monocyte phenotype shifts (i.e. expansion of CD14dim and CD16 bright subpopulations which have features in common with mature tissue macrophages) • Macrophages of aged mice may produce less IFN-, less nitric oxide synthetase, and hydrogen peroxide.

24. Table 15-15 Aging-Related Changes in Natural Killer (NK) Cells • General decline in cell function • Good correlation between mortality risk and NK cell number • Increased in proportion of cells with high NK activity (i.e. CD16+, CD57-) • Progressive increase in percentage of NK cells • Impairment of cytotoxic capacity per NK cell • Increase in NK cells having surface molecule CD56 • dim subset

25. Table 15-10 Some Aging-Related Shifts in Cytokines • Increased proinflammatory cytokines IL-1, IL-6, TNF- • Increased cytokine production imbalance • Decreased IL-2 production • Increased production of IL-8, which can recruit macrophages and may lead to pulmonary inflammation • Increase in dysfunctional IL-8 • Decreased secretion of IFN- (interferon) • Altered cytokine responsiveness of NK cells, which have decreased functional abilities • Increased levels of IL-10 and IL-12 upregulated by Antigen Processing Cells

27. Table 15-17 Major Diseases Associated with Aging • in Immune Function • Increased tumor incidence and cancer • Increased incidence of infectious diseases caused by: • E. Coli • Streptococcus pneumonia • Mycobacterium tuberculosis • Pseudomonas aeruginosa • Herpes virus • Gastroenteritis, bronchitis, and influenza • Reappearance of latent viral infection • Autoimmune diseases and inflammatory reactions: • Arthritis • Diabetes • Osteoporosis • Dementia

28. Table 15-9 Hallmarks of Immunosenescence • Atrophy of the thymus: • decreased size • decreased cellularity (fewer thymocytes and epithelial cells) • morphologic disorganization • Decline in the production of new cells from the bone marrow • Decline in the number of cells exported by the thymus gland • Decline in responsiveness to vaccines • Reduction in formation and reactivity of germinal center nodules in lymph nodes where B-cells proliferate • Decreased immune surveillance by T lymphocytes and NK cells

29. TABLE 15.6 - CHEMICAL MEDIATORS OR MODULATORS CYTOKINES - influence proliferation, differentiation, and survival of lymphoid cells; has numerous actions on other body cells, compromises the following: Granulocyte-Macrophage Colony Stimulating Factor (GM-CSF):regulates hematopoiesis, affects phagocyte function and angiogenesis Interleukin (IL):family, 16 different proteins from IL1 and up; numerous effects on lymphocytes and other cells with IL receptors Colony Stimulating Factor (CSF):glycoprotein regulating white blood cell production, activity, and survival Tumor Necrosis Factor (TNF):1) TNF- cytotoxic against malignant and inflammatory cells; produced primarily by macrophages, 2) TNF- cytotoxic against malignant cells; enhances phagocytosis; produced primarily by T cells Interferon (IFN): 1) IFN-,: produced by many cells; antiviral actions, 2) IFN-:synthesized by activated NK and T cells; involved in activation of macrophages and inflammation

30. 15-11 Additional Aging-Related Shifts in Immune Functions • Altered membrane fluidity • Increased apoptosis perhaps due to decline • in CD28 expression and IL-2 production • CD20 overexpression on lymphocytes • Increased CAMs expression on lymphocytes • Old cells may have greater levels of • messenger RNA for 3 mitotic inhibitors • Decrease number of HLA class I and II • antigenic sites on lymphocytes • Increase in activated T-cell expressing DR molecules • Decreased proportion of T, B, and NK cells • expressing CD62L and increased density per cell • of this adhesion receptor expression • Upregulation of L-selectin per T-cell • Shift in lymphocyte population to contain • more CD3-NK cells and CD3+CD56+ T-cells • CD3 downregulation and CD50 upregulation • on T-cells affecting activation and proliferation • Increased T-cell death by fas/fas-ligand mediated • response in presence of IL-2 • Heightened density of CD5 on B-cells • Decreased number of monocytes with LFA-1 • Decreased ability of dendritic cells to stimulate • T-cell secretion of IFN- and IL2