Transcript Immune System

The Body Defenses
Body Defense Overview
• Innate Immunity
– Barrier Defenses
– Internal Defenses
• Acquired Immunity
– Humoral Response
– Cell-mediated
Response
Innate Immunity in Invertebrates
(Nonspecific)
• Chitin (physical
barrier) in intestine
• Lysozymes and low
pH (digests microbial
cell walls)
• Hemocytes in
hemolymph
– Phagocytosis
– Antimicrobial peptides
Innate Immunity in Vertebrates
Barrier Defenses (Nonspecific)
• Skin
– Physical Barrier &
Lysozymes
• Digestive Tract
– High acidity & normal
bacteria
• Respiratory Tract
– Mucus & Cilia
• Genitourinary Tract
– Acidity of Urine
Innate Immunity in Vertebrates
Internal Defenses
(Nonspecific)
• Phagocytic White
Blood Cells
• The Inflammatory
Response
• Antimicrobial
Proteins
• Natural Killer Cells
Phagocytic White Blood Cells
(Leukocytes)
• Neutrophils (70%)
– short lived
• Monocytes (5%)
– macrophages
– long lived in lymphatic tissue
• Eosinophils (1.5%)
– attack larger parasites
The Inflammatory Response
• Releases histamine
– (basophils and mast cells)
• Allows for dilation and increased permeability
• Increased temp due to increased blood flow
• Cytokines (protein) direct migration of
Phagocytes (activate lymphocytes)
Antimicrobial Proteins
• Compliment System
–
–
–
–
30 proteins
lyses viruses and pathogens
may attract phagocytes and cause adherence
Two pathways
• Alternative
– triggered by substances on invaders and does not use
antibodies
• Classical
– triggered by antigens and uses antibodies
Antimicrobial Proteins
• Interferon
– proteins secreted by viral infected cells
– diffuse to surrounding cells
– surrounding cells make chemicals that inhibit
viral reproduction
Natural Killer Cells
• Recognize damaged or diseased cells
– Class 1 MHC molecule on surface of most cells
– Missing when diseased
• Release chemical to destroy cells lacking this
protein
Acquired Immunity
• Vertebrates
– Uses Lymphocytes to recognize antigens
– Two major types
• B lymphocytes
• T lymphocytes
The
Development of
Lymphocytes
• B cells
– made and mature in
bone marrow
• T cells
– made in bone
marrow and matures
in thymus
Epitopes
• Antigenic determinant (special areas on
antigens
– Usually has several
Antigen Recognition by
Lymphocytes
• B Cells – Y shaped receptors made up of
4 polypeptide chains (two heavy / two
light)
• Recognize intact antigens
Antigen Recognition by
Lymphocytes
• T Cells – 2 polypeptide chains (an alpha
chain and a beta chain)
• Recognize small fragments of antigens
Major Histocompatibility Complex
• Class 1 MHC
molecules
– Work with
Cytotoxic T cells
• Class 2 MHC
molecules
– Work with both
Cytotoxic T Cells
Helper T cells
Immune Response
• Primary Immune
Response
– Takes 10 - 17 days
from initial exposure to
an antigen
– Produces B and T
cells
• Secondary Immune
Response
– takes 2 - 7 days from
re-exposure to antigen
Immune Responses
• Humoral Immunity
– involves B cells
– produces antibodies
that circulate in the
blood, plasma and
lymph
– cells do not have to be
next to antigen to
attack
• Cell-mediated
Immunity
– involves T cells
– cells must be next to
antigens to attack
Response to Nearly All Antigens
• Helper T cells
– attach to macrophage that has attacked an
antigen
• often uses CD4 receptors
– releases interleukin (Cytokine)
– activates Cytotoxic T cells and Plasma B cells
Cell-mediated Response
• Cytotoxic T cells
–
–
–
–
–
attach to infected cells / Cancer Cells
Usually uses a CD8 receptor
perforin (protein) makes a pore in membrane
ions and water enters pores
infected cell lyses
B Cells: A Response to
Extracellular Pathogens
– Response to
extracellular
pathogens
– Plasma B cells
produce antibodies
– Memory B cells
live a long time
and can help
produce other B
cells quickly when
re-infected by the
same antigen
Antibodies
• A group of globular
serum proteins called
immunoglobulins
Immunity in Health and Disease
• Active Immunity
– Getting the disease
– Immunizations
(Vaccinations)
• Passive Immunity
– Antibodies transferred
from one individual to
another
• pregnancy and breast
feeding
• injection of antibodies
Abnormal Immune
Function
• Allergies
– hypersensitive responses to
antigens
– anaphylactic shock
• Autoimmune Diseases
– immune system attacks own
body
• Lupus, MS, ALS, Rheumatoid
Arthritis
• Immunodeficiency Diseases
– lowered immune system
– SCIDS, AIDS
Stages
of HIV
Infections