Immune System

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Immune System
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Major Characteristics

• Self-recognition- no immune response to own cells
• Specificity- immune response to single foreign
  antigen
• Memory- develop immunity

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Review of Structure and Function

• Lymphoid Organs
• Red Bone Marrow- leukocyte
• stem cells
• 2. Thymus - lymphoid organ,
• lymphocyte maturation
• thymopoeitin and thymosin
• 3. Spleen - lymphocyte maturation
• 4. Lymph Nodes - filter lymph
• 5. Tonsils - palatine, lingual, pharyngeal
  (adenoids)

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Review of Structure and Function
Lymphoid Cells Lymphocytes B Lymphocytes (B
Cells) T Lymphocytes Helper T Cells
(TH) Cytotoxic T Cells (TC) Phagocytes Monocyte
s/Macrophages Neutrophils
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The Immune Response
Antigen - substance that induces an immune
response Self Antigens - major
histocompatibility complex (MHC-1) Antigen
Presenting Cells - e.g. Langerhans Cells,
dendritic cells, macrophages, activated B
lymphocytes Antibodies Immunoglobulins,
soluble in blood plasma 1. Humoral Response -
clonal selection of B-lymphocyte (memory cell)
matures to plasma cell, secretes Abs
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Immune Response (cont.)
2. Cellular-Mediated Response T
Lymphocytes Cytotoxic T Cells Natural Killer
Cells (NK cells) Antigen Presenting Cell MHC-1
present fragments of cellular protein MHC-2
surface of B-lymphocytes, macrophages
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Age Related Changes
Bone Marrow - reduction in active stem cells with
age Thymus - most dramatic changes decrease
mass with age (involution) max. in early
childhood, decreases from teens thru
adulthood 10 of original size by age
50 decrease secretion of thymosin,
thymopoetin decrease ability of T Lymphocytes to
mature activation of T Cells declines decline
in T helper cells, dec. B Cell activation
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180.00
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Age Related Changes (cont.)
Spleen - Decline in mass of spleen Decline in
Lymphoid tissue People who have undergone a
splenectomy have an increase in life expectancy
! Lymph Nodes - loss of lymphoid
tissue replaced with connective tissue
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Age Related Dysfunction
Apparent Contradiction Overall Decline in
Immune Response with age But, Increase in
autoimmune disease Autoimmune - loss of ability
to recognize self (i.e. own tissue recognized as
foreign) proteins degraded now recognized as
foreign ? e.g. rheumatoid arthritis new viruses
trigger mistakes in immune system ?
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Age related T-Cell Defects
Reduction in activity compromises immune
function Disease increases in frequency in the
elderly e.g. Non-Hodgkins lymphoma tuberculosi
s shingles chronic lymphocytic leukemia
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Immune Senescence
Hormonal ? Can be partially reversed with
thymopoetin Age of mice Thymopoetin?
competent cells 2 mos. No 5916 24
mos. No 385 24 mos. Yes 977 proximate
vs. ultimate causation