human anatomy and physiology immunology: adaptive defenses
TRANSCRIPT
Human Anatomy and Physiology
Immunology: Adaptive defenses
Overview
System must be primed before it can take effect
1800 experiment Inject a bacteria into an animal It raises proteins (antibodies against the
infection Serum containing antibodies protects other
animals not previously exposed
Overview
Characteristics of adaptive response Specific recognition of pathogens Response is systemic Response has memory (mounts a stronger
attack on subsequent exposure) Injecting lymphocytes also offered protection
Types of immunity
1. Humoral Antibodies produced from lymphocytes
present in body as ‘humor’ 2. Cellular
Lymphocytes themselves defend the body
Antigens
Substances provoking an immune response (i.e. any foreign cell)
Not normally present in body, therefore ‘nonself’
Self recognition Major histocompatibility complex (MHC) class I
proteins - all cells except RBCs MHC class II proteins (on APC cells)
Humoral immunity
Humoral immunity
Clonal selection- Steps B-cells clone themselves upon encountering an antigen
(1° response, 3 - 6 days) Resulting plasma cells secrete antibodies into plasma Clone cells not differentiating into plasma cells become memory cells
Re-infection produces a 2° response
B-cell cloning
Humoral responses
Antibody structure Immunoglobulins (Ig)
4 polypeptides 2H, 2 L (disulphide bonds) Antibody monomer, T or Y shaped 2 antigen binding sites C (constant) region V (variable) region
Antibody classes
Classification based on C region in heavy chain IgD, IgG, IgE, IgA, and IgM
pentamerdimer
monomer
Antibody functions
Antibodies inactivate antigens and tag them for destruction
Strategies Neutralization Agglutination Precipitation Complement
Humoral immunity
Active - natural vs. artificially acquisition, memory B cells Long term protection
Passive - not challenged by antigens, no memory B cells Short term protection. From
mother several months, gamma globulin (gG) weeks.
Cells of adaptive immunity 1. Lymphocytes (B cells, T cells) T cells (immunocompetent in thymus)
B cells (immunocompetent in bone marrow)
Cells of adaptive immunity 2. Antigen-presenting cells (APC)
Engulf antigens, present fragments to Tc-cells to destroy
e.g. CT - dendritic cells, skin - Langerhans’ cells, lymph - macrophages
Cell-mediated immunity 2 types of T-cells, CD4
(TH) and CD8 (TC) T-cells activate by
double recognition V region binds to an
antigen, also recognize self (MHC class I proteins)
Cell-mediated immunity Helper T Cells
Bind to APC and help stimulate T cell and B cell proliferation using interleukin-2 (hormone)
Clinical connections 1. Organ transplants
Tissue similarity so that Tc cells, NK cells and antibodies do not attack the new organ
Immunosuppressive therapy Anti-inflammatory drugs Immunosuppressant drugs
2. Immunodeficiencies Immune cells, phagocytes, complement behave
abnormally AIDS/HIV - helper T cells destroyed
Clinical connections
3. Autoimmune diseases - loss of ability to distinguish self from non-self. Body produces antibodies against its own cells MS: destroys white matter of brain and spinal cord Type-1 diabetes: destroys pancreatic ß cells
4. Allergies Anaphylaxis: basophils and mast cells become
oversensitized to allergens, resulting in histamine release causing inflammation
Anaphylactic shock