The Immune System

Widely dispersed system

Review of structure and function

located in marrow cavities of bones

yellow vs. red marrow

hematopoiesis

bone marrow

The Immune System

Review of structure and function

location

consists of lymphocytes and macrophages

“gives” immunocompetence to T lymphocytes via thymosins

thymus gland

The Immune System

location

red vs. white pulp

functions

spleen

Review of structure and function

The Immune System

locations

structure

function

lymph nodes

Review of structure and function

The Immune System

locations

functions

tonsils

Review of structure and function

The Immune System

What is immunity?

origin and immunocompetence

T cells (cancer cells, transplants, bacteria, virus-laden cells)

lymphocytes and plasma cells

Review of structure and function

cytotoxic T cells

helper T cells

suppressor T cells

memory T cells

B cells (viruses, bacteria)

plasma cells

memory B cells

The Immune System

locations

primary immune response

secondary (anamnestic) response

lymphocytes and plasma cells

Review of structure and function

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

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

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

decrease in precursor cells

decreased differentiation into T- and B-cells

increased suppressor T-cells

increased factors that inhibit immunity (?)

Age-related dysfunctions in the

immune system General decrease in immune responses decreased immune sensitivity

increased autoimmunity

causes

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

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 2:1

at ratio of 1:1 AIDS symptoms begin to appear

at ratio of 0.5:1, full-blown disease

Lymphomas

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