AP Biology: ch43 Immune Flashcards
Innate immunity
Is present before any exposure to pathogens and is effective from the time of birth
Involves nonspecific responses to pathogens
Acquired immunity ( aka adaptive)
after exposure to inducing agents such as microbes, toxins, or other foreign substances
Very specific response to pathogens
INNATE IMMUNITY- BROAD DEFENSE
Broken down into:
- external defenses
2. Internal Defenses: cellular and chemical mechanisms
External defense:
- Intact skin and mucous membranes
Form physical barriers that bar the entry of microorganisms and viruses
Secretions:
Mucus production- viscous and traps particles
Tears- contain lysosome
Oil and sweat glands- acidic
In the trachea, ciliated epithelial cells
Sweep mucus and any entrapped microbes upward, preventing the microbes from entering the lungs
Internal cellular defenses
Depend mainly on phagocytosis
Phagocytes, types of white blood cells
Ingest invading microorganisms
Initiate the inflammatory response
Phagocytes attach to their prey via surface receptors
And engulf them, forming a vacuole that fuses with a lysosome
Macrophages, a specific type of phagocyte
Can be found migrating through the body
Can be found in various organs of the lymphatic system
The lymphatic system
Plays an active role in defending the body from pathogens
Antimicrobial Proteins- Internal Innate Immunity
Attack microbes directly of impede their reproduction
Complement System: made of 30 different proteins
causes lysis of invading cells and help trigger inflammation
Interferons ( alpha and beta)
Secreted by virus infected cells and cause other cells to inhibit viral reproduction
Histamine and other chemicals released from injured cells
Promote changes in blood vessels that allow more fluid, more phagocytes, and antimicrobial proteins to enter the tissues
Natural killer (NK) cells
Patrol the body and attack virus-infected body cells and cancer cells
Trigger apoptosis in the cells they attack
Many invertebrates defend themselves from infection
Sea stars: ameboid cells do phagocytosis
Insect exoskeleton, mucous membrane- external barrier
Insects hemolymph- contains hemocytes which ingest bacteria
lymphocytes provide specific defenses against infection
Triggered after innate immunity is turned on
Cytokines- chemicals released from phagocytes that activate lymphocytes
An antigen is any foreign molecule
recognized by lymphocytes and elicits a response from them
A lymphocyte actually recognizes
and binds to specific site called epitope
The vertebrate body is populated by two main types of lymphocytes
B lymphocytes (B cells) and T lymphocytes (T cells)
Circulate through blood
Concentrated in spleen, lymph nodes, and other lymph tissue
Each cell only one type of antigen
B Cell Receptors for Antigens
Two specific binding sites- attach to whole antigens
Are often called membrane antibodies or membrane immunoglobulins
T Cell Receptors for Antigens and the Role of the MHC
Consists of two different polypeptide chains
Single antigen binding site for each
T cell receptors
T cells bind to small fragments of antigens
That are bound to normal cell-surface proteins called MHC molecules
MHC molecules
Are encoded by a family of genes called the major histocompatibility complex
Infected cells produce MHC molecules
Antigen presentation: antigen fragments bound and transported to the cell surface
A nearby T cell
Can then detect the antigen fragment displayed on the cell’s surface
Class I MHC- nucleated cells that have been infected or turned cancerous
Display peptide antigens to cytotoxic T cells ( kills cells when activated)
CLASS II MHC in dendritic, macrophages and B cells
Obtain antigens through phagocytosis
Display antigens to helper T cells
MHC importance
Family of genes to encode for MHC ( at least 6)
Most polymorphic allele sets per person
Most people heterozygous for EACH gene
Each person has a MHC fingerprint
As many genes as possible to match when doing organ transplants
LYMPHOCYTES:
develop in bone marrow
Newly formed lymphocytes are all alike
But they later develop into B cells or T cells, depending on where they continue their maturation
As B and T cells are maturing in the bone and thymus
Their antigen receptors are tested for possible self-reactivity
Lymphocytes bearing receptors for antigens already present in the body
Are destroyed by apoptosis or rendered nonfunctional
In a primary immune response
Clonal selection: Binding of antigen to a mature lymphocyte induces lymphocyte proliferation and differentiation
Peaks at 10- 17 days
Clonal B Cell Selection
Generates a clone of short-lived activated effector cells and a clone of long-lived memory cells
SECONDARY IMMUNE RESPONSE
Memory cells facilitate a faster, more efficient response
Humoral immune response
activation and clonal selection of B cells, production of secreted antibodies
Cell-mediated immune response
activation and clonal selection of cytotoxic T cells
Helper T cells produce CD4, a surface protein
Helps Helper T to bind to class II MHC molecule–antigen Activation of the helper T cell then occurs
Cytotoxic T Cells: eliminate infected and cancer cells
Bind to Class I MHC antigen on target cell
make CD8
protein that enhances the interaction between a target cell and a cytotoxic T cell
Activated cell releases perforin to make holes in cell and proteolytic enzymes (granzymes) to kill cell
Activation of B cells
Is aided by cytokines and antigen binding to helper T cells
B cell clonal selection
Generates antibody-secreting plasma cells
Class II MHC molecules + CD4 displayed ON macrophage after phagocytosis
Helper T cell produces clones
Helper T activates B cell with help of cytokines from T cell
B cell clonal selection to make
memory B cells and Plasma cells which secrete antibody
The binding of antibodies to antigens
Leads to elimination of microbes by phagocytosis and complement-mediated lysis
Active Immunity
Develops naturally in response to an infection
Or by immunization, also called vaccination ( uses nonpathogenic form or part of a microbe to create an immune response and create memory cells)
Immediate, short-term protection
Is conferred naturally when IgG crosses the placenta from mother to fetus or when IgA passes from mother to infant in breast milk
Can be conferred artificially by injecting antibodies into a nonimmune person
Certain antigens on red blood cells
Determine whether a person has type A, B, AB, or O blood
Opposite antibody is present in serum
Recipient-donor combinations
Can be fatal or safe
Another red blood cell antigen, the Rh factor
Creates difficulties when an Rh-negative mother carries successive Rh-positive fetuses
Mother can mount a immune reaction against the fetus
Later pregnancies of Rh + fetus – mother has memory cells which can destroy baby RBC
Preventable- mom can be injected with Anti-Rh IgG antibodies
MHC molecules
Are responsible for stimulating the rejection of tissue grafts and organ transplants
The chances of successful transplantation are increased
If the donor and recipient MHC tissue types are well matched
If the recipient is given immunosuppressive drugs
Allergies are exaggerated (hypersensitive) responses
To certain antigens called allergens
Originally a response to parasitic worms?
Antibodies are released in response to pollen etc
If pollen gets in launches histamine for full inflammatory response
An acute allergic response sometimes leads to anaphylactic shock
A whole-body, life-threatening reaction that can occur within seconds of exposure to an allergen
ANAPHYLATIC SHOCK
Acute allergic response
Mast cells all drop granules causing massive blood vessel dilation
Blood pressure drops
Death can happen in a few minutes
Epi pen- counteracts blood vessel dilation
Autoimmune Diseases
The immune system loses tolerance for self and turns against certain molecules of the body
Lupus- antibodies ( autoantibodies) against histones and DNA that is being released from broken down cells
Rheumatoid arthritis
Leads to damage and painful inflammation of the cartilage and bone of joints
Other examples of autoimmune diseases include
Multiple sclerosis
Insulin-dependent diabetes
Crohns disease
Immunodeficiency Diseases
Inability to protect body from pathogens or cancer cells
An acquired or secondary immunodeficiency
In severe combined immunodeficiency (SCID)
Called Bubbly Boy syndrome
Both the humoral and cell-mediated branches of acquired immunity fail to function
People with AIDS
Are highly susceptible to opportunistic infections and cancers
Arises from the loss of helper T cells
Both humoral and cell-mediated immune responses are impaired
The loss of helper T cells
Results from infection by the human immunodeficiency virus (HIV)
