The Immune SystemChapter 43

Overview Innate vs. Acquired Immunity

Innate Immunity:Present from the time of birthNonspecificExternal barriers, Mucous membranes, macrophages

Acquired Immunity: Highly specific Humoral response (antibodies) Cell-mediated response (cytotoxic lymphocytes)

Innate vs. Acquired Immunity

43 ~1 Innate Immunity External Defenses:

Skin Acidic pHPhysical barrier

Mucous membranesTraps microbes

Antimicobial Proteins - Lysozyme Enzyme that destroys bacteria

Internal Cellular & Chemical Defenses

PhagocytosisThe ingestion of invading microorganisms by certain

types of white blood cells4 white blood cells are phagocytic

Neutrophils Macrophages Eosinophils Dendritic cells

Phagocytosis

Lymphatic system

Internal Cellular & Chemical Defenses

Antimicrobial ProteinsAttack microbes LysozymeComplement system – 30 proteins that activate

when microbes invade Interferon – protection against viral infection by

limiting cell to cell reproduction

Internal Cellular & Chemical Defenses

Inflammatory Response – damage to tissue by physical injuryHistamine causes increased blood flow to the inured

site (redness & heat = inflammation)Help deliver antimicrobial proteins and clotting

elements to the injured site

Inflammatory Response

Internal Cellular & Chemical Defenses

Natural Killer CellsPatrol the body and attack virus-infected body cells

and cancer cellsApoptosis – NK cells release chemicals that lead to

death of the cell by apoptosis (programmed cell death)

43 ~ 2 Acquired Immunity

Activates Lymphocytes

Antigen – any foreign molecule that is specifically recognized by lymphocytes and elicits a response from them

2 main types of lymphocytesB lymphocytes (B cells)T lymphocytes (T cells)Both circulate through the blood and lymph and are

concentrated in the spleen, lymph nodes, and other lymphoid tissue

Lymphocyte development

Originate from pluripotent stem cells in the bone marrow

T cells develop in the Thymus

B cells remain in bone marrow and complete maturation there

Lymphocyte development

Primary vs. Secondary Immune response

Primary immune response: occurs the first time the body is exposed to a particular antigenPeaks about 10-17 days after exposure

Secondary Immune response: occurs after a second exposure to the same antigenFasterGreater magnitudeMore prolonged

Primary vs. Secondary Immune response

43.3 ~ Humoral & Cell-mediated response

Humoral immune response – involves the activation and clonal selection of B cells, resulting in production of secreted antibodies that circulate in the blood and lymph

Cell-mediated immune response – involves the activation and clonal selection of cytotoxic T cells which directly destroy certain target cells.

Humoral vs. cell-mediated immune response

43.4 ~ Distinguishing self from non-self

Blood groups and transfusions

Tissue and organ transplants

Blood groups & Transfusions

A, B, AB, and O blood groups

A red blood cells have A antigens on their surface and make antibodies against the B antigen.

Transfusion reaction – chills, fever, shock and kidney malfunction

AB = universal recipient

O = universal donor

Rh negative mother carries a fetus that is Rh positive mother mounts a humoral response. Danger occurs in subsequent pregnancies with Rh positive fetus.

Tissue & Organ Transplants

A rejection reaction is mounted in most graft and transplant recipients because molecules are foreign.

No danger of rejection if the donor and recipient are identical twins or if tissue is grafted from another part of the same person’s body.

43.5 ~ Immune system Diseases

Allergies – are exaggerated (hypersensitive) responses to certain antigens called allergens

Typical allergy symptoms: sneezing, runny nose, tearing eyes, and smooth muscle contractions

Anaphylactic shock – acute allergic response leads to a whole-body life-threatening reactions. Responses to bee venom, penicillin, peanuts, fish

Epinephrine (epipen) counteracts this allergic response

Autoimmune Diseases: The immune system loses tolerance for self and turns against certain moleculesLupus – skin rashes, fever, arthritis, and kidney

dysfunctionRheumatoid arthritis – painful inflammation of

cartilage and bond of jointsMultiple Sclerosis – T cells enter CS and destroy

myeline sheath

Arise from some failure in immune system regulation

Immunodeficiency Diseases: The inability of the immune system to protect the body from pathogens or cancer cells that it should normally Inborn (SCID) vs. acquired (AIDS)

Stress & the Immune System: Healthy immune function depends on both the endocrine system and nervous systemHormones secreted by the adrenal glands during

stress affect the # of white blood cells and can suppress the immune system

Acquired Immunodeficiency Syndrome (AIDS): Highly susceptible to infections (Pneumonia, bronchitis)

Loss of helper T cells both humoral and cell-mediated are imparied

Results from infection by HIV (retrovirus)