biology of human aging chapter 10 the immune system
TRANSCRIPT
BIOLOGY OF HUMAN AGING
CHAPTER 10 CHAPTER 10
The Immune System
Outline Review of structure and function
Bone marrow/thymus/spleen/lymph nodes/tonsils/lymphocytes & plasma cells
Age related changesBone marrow/thymus/spleen/lymph nodes/tonsils
Age related dysfunctions General decrease in immune responses Age associated T-lymphocyte defects Acquired immune deficiency syndrome Lymphomas
Introduction People become more susceptible to disease as they
get older.
Immune system is a major defense against invasion of the body by microorganisms
Deficiencies of immune system make us more vulnerable to disease
Several facets of the immune response decrease with age
Review of Structure and FunctionBone Marrow•Located in central cavities of bones•Two types: yellow (fat deposit), red (hematopoiesis)
Thymus•Mass of lymphoid tissue•Located beneath the sternum•(consists of lymphocytes)
Spleen Largest lymphoid organ
Lies left of the stomach and extends upward to diaphragm
Composed of red pulp (blood sinuses and blood cells) and
white pulp (lymphocytes)
Filters the blood
Removes old, abnormal, or damaged RBCs
Lymph nodes Small masses of lymphoid tissue Located along lymphatic vessels Lymph enters the nodes and slowly filters through
the sinuses
Tonsils Small masses of lymphoid tissue embedded in the
lining of the pharynx and nasopharynx
Lymphatic System
Lymphatic and Immune System
Functions: Defends against infection: bacteria, fungi, viruses,
etc. Destruction of cancer and foreign cells. Synthesis of antibodies and other immune
molecules. Production of white blood cells.
Hematopoiesis: blood cell production
Development of T and B Lymphocytes
Third Line of Defense: The Immune Response (Specific Immunity)
Immunity: “Free from burden”. Ability of an organism to recognize and defend itself against specific pathogens or antigens.
Immune Response: Involves production of anti-bodies and generation of specialized lymphocytes against specific antigens.
Antigen: Molecules from a pathogen or foreign organism that provoke a specific immune response.
The Immune Response Destroys Specific Invaders
Antigen: Molecule that elicits an immune response.
“Antibody generating” Microbial antigens: Viral capsid, bacterial call wall, etc. Nonmicrobial antigens: Pollen, latex, food, etc.
Antibody: Protein found in blood plasma that attaches to antigen and helps counteract its effects.
Vaccination or Immunization: Process in which harmless forms of antigen or pathogen are introduced into body to provoke an immune response.
Lymphocytes Mount a Dual Defense1. Cell Mediated Immunity Immunity that requires cell to cell contact. Carried out by T cells:
Develop in the thymus. T cytotoxic cells: Important in defense against:
Cancer cells Self cells infected with fungi, viruses, protozoans, and
bacteria. T helper cells: Play a central role in immunity.
Act indirectly by controlling the immune functions of other cells:
Increased antibody production by B cells. Increased phagocytosis by macrophages. Increased killing of foreign and cancer cells.
T helper cells play a central role in immunity
Lymphocytes Mount a Dual Defense
2. Humoral (Antibody Mediated) Immunity Antibodies are found in our body fluids:
Blood Lymph Interstitial fluid
Antibodies are produced by B cells. B cells develop in bone marrow.
Antibodies are specific molecules that circulate through out our body and attach to foreign antigens, marking them for destruction.
Age-related changesBone Marrow• Reduction in the amount of active red bone marrow• Stem cells remain insufficient amounts to reproduce adequately
Thymus• Degeneration and reduction of size with aging • Lesser amounts of thymosins hormone produced (thought to be
responsible for the T cells differentiation)• Decrease in activity and numbers in Helper T cells• Increased number of immature T cells• Decreased activation of T cells• No change in total number of B cells, yet decline in antibody
production• Lower resistance to viral infections
Spleen• The average weight decreases. (animal studies!)• Lymphoid tissue gradually diminishes after puberty.• The nodes of older individuals contain more macrophages.
Lymph Nodes• Lymphoid tissue maximum development during childhood,
gradually diminish after puberty
Tonsils• Tend to decrease in size with age (palatine/pharyngeal tonsils).• Significant decrease in the lymphocyte number with age
Age-related Dysfunctions
General decrease in Immune Responses Reduction in cell mediated humoral immune responses Increased tendency for the development of autoimmune
reactions Diminished ability of the Abs to recognize Mutation of stem cells More suppressor cells or factors that inhibit immune
responses
Age-Associated T-Lymphocyte Defects: Reduced activity of T lymphocytes Reduced cell mediated immunity Reactivation of lymphoma, tuberculosis, and shingles
LymphomasSwollen lymph nodes, persistent fever, night sweats & weight lossClassification is based on patterns of spread, clinical behavior, and cells of origin
Acquired Immune Deficiency Syndrome
Immunodeficiency: depression of immune system and lack or insufficiency of immune responses
Helper T cells- CD4 Mode of transmission Dormancy Symptoms: generalized lymph node swelling, persistent
fever, night sweats, diarrhea, and severe weight loss AIDS-related complex: pneumonia and Kaposi’s sarcoma