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The Immune System

Widely dispersed system

Review of structure and function

bone marrow
 located in marrow cavities of
bones
 yellow vs. red marrow
 hematopoiesis
The Immune System

Review of structure and function

thymus gland
 location
 consists of lymphocytes and
macrophages
 “gives” immunocompetence to
T lymphocytes via thymosins
The Immune System

Review of structure and function

spleen
 location
 red vs. white pulp
 functions
The Immune System

Review of structure and function

lymph nodes
 locations
 structure
 function
The Immune System

Review of structure and function

tonsils
 locations
 functions
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
 suppressor T cells
 helper T cells
 memory T cells
 B cells (viruses, bacteria)
 plasma cells
 memory B cells
The Immune System

Review of structure and function

lymphocytes and plasma cells
 locations
 primary immune response
 secondary (anamnestic) response
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

unclear about functional losses
palatine tonsils decrease gradually; pharyngeal
tonsil (adenoid) atrophies completely
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 (?)
Age-related dysfunctions in the
immune system

Age-associated T-lymphocyte defects


T-cell numbers decrease with age

immunosuppressive treatment has same effect
diseases normally held in check by T-cells are
allowed to appear
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
