The Immune System u Widely dispersed system u Review of structure and function F located in marrow cavities of bones F yellow vs. red marrow F hematopoiesis ¶ bone marrow

The Immune System u Review of structure and function F location F consists of lymphocytes and macrophages F “gives” immunocompetence to T lymphocytes via thymosins · thymus gland

The Immune System F location F red vs. white pulp F functions ¸ spleen u Review of structure and function

The Immune System F locations F structure F function ¹ lymph nodes u Review of structure and function

The Immune System F locations F functions º tonsils u Review of structure and function

The Immune System F What is immunity? F origin and immunocompetence F T cells (cancer cells, transplants, bacteria, virus-laden cells) » lymphocytes and plasma cells u Review of structure and function ä cytotoxic T cells ä helper T cells ä suppressor T cells ä memory T cells F B cells (viruses, bacteria) ä plasma cells ä memory B cells

The Immune System F locations F primary immune response F secondary (anamnestic) response » lymphocytes and plasma cells u Review of structure and function

Age-related changes in the immune system u All lymphoid tissues decreases in mass and efficiency with age u Bone marrow u Thymus gland ¶ puberty to 50, lose 90% of mass · loss of size = loss of thymosins ¸ new T cell immunocompetence decreases

Age-related changes in the immune system u B cells ¶ no decline with age · decreased responsiveness to antigens ¸ by 70, 85% reduction in antibody production ¸ B cell changes may be result of decreased helper T cell numbers

Age-related changes in the immune system u Spleen u Lymph nodes u Tonsils ¶ reach maximum size at 12 · palatine tonsils decrease gradually; pharyngeal tonsil (adenoid) atrophies completely ¸ unclear about functional losses

F decrease in precursor cells F decreased differentiation into T- and B-cells F increased suppressor T-cells F increased factors that inhibit immunity (?) Age-related dysfunctions in the immune system u General decrease in immune responses ¶ decreased immune sensitivity · increased autoimmunity ¸ causes

Age-related dysfunctions in the immune system u Age-associated T-lymphocyte defects ¶ T-cell numbers decrease with age · diseases normally held in check by T-cells are allowed to appear ¸ immunosuppressive treatment has same effect

Age-related dysfunctions in the immune system u Acquired immune deficiency syndrome ¶ HIV infects helper T-cells (CD4 cells), ultimately killing them · alters ratio between helper T-cells and suppressor T-cells ¸ normal ratio is 2:1 ¹ at ratio of 1:1 AIDS symptoms begin to appear º at ratio of 0.5:1, full-blown disease u Lymphomas

Take home messages about immunity u decreased lymphoid tissue body-wide u general decline in immunity u decreased T cell number u decreased B cell activity u increased incidences of autoimmune responses