The Immune System

1
The Immune System

• Widely dispersed system
• Review of structure and function

• bone marrow

• located in marrow cavities of bones
• yellow vs. red marrow
• hematopoiesis

2
The Immune System

• Review of structure and function

• thymus gland

• location
• consists of lymphocytes and macrophages
• gives immunocompetence to T lymphocytes via
  thymosins

3
The Immune System

• Review of structure and function

• spleen

• location
• red vs. white pulp
• functions

4
The Immune System

• Review of structure and function

• lymph nodes

• locations
• structure
• function

5
The Immune System

• Review of structure and function

• tonsils

• locations
• functions

6
The Immune System

• Review of structure and function

• lymphocytes and plasma cells

• What is immunity?
• origin and immunocompetence
• T cells (cancer cells, transplants, bacteria,
  virus-laden cells)

• cytotoxic T cells
• helper T cells

• suppressor T cells
• memory T cells

• B cells (viruses, bacteria)

• plasma cells
• memory B cells

7
The Immune System

• Review of structure and function

• lymphocytes and plasma cells

• locations
• primary immune response
• secondary (anamnestic) response

8
Age-related changes in the immune system

• All lymphoid tissues decreases in mass and
  efficiency with age
• Bone marrow
• Thymus gland

• puberty to 50, lose 90 of mass
• loss of size loss of thymosins
• new T cell immunocompetence decreases

9
Age-related changes in the immune system

• 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

10
Age-related changes in the immune system

• Spleen
• Lymph nodes
• Tonsils

• reach maximum size at 12
• palatine tonsils decrease gradually pharyngeal
  tonsil (adenoid) atrophies completely
• unclear about functional losses

11
Age-related dysfunctions in the immune system

• General decrease in immune responses

• decreased immune sensitivity
• increased autoimmunity
• causes

• decrease in precursor cells
• decreased differentiation into T- and B-cells
• increased suppressor T-cells
• increased factors that inhibit immunity (?)

12
Age-related dysfunctions in the immune system

• 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

13
Age-related dysfunctions in the immune system

• 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 21
• at ratio of 11 AIDS symptoms begin to appear
• at ratio of 0.51, full-blown disease

• Lymphomas

14
Take home messages about immunity

• decreased lymphoid tissue body-wide
• general decline in immunity
• decreased T cell number
• decreased B cell activity
• increased incidences of autoimmune responses