Ch 43 immune system
1 / 34

Ch 43- Immune system - PowerPoint PPT Presentation

  • Uploaded on
  • Presentation posted in: General

Ch 43- Immune system. Immune system. Defends body against disease Pathogens – agents of disease (bacteria, viruses, protists ) Non specific immunity (innate immunity) All animals & plants have defenses effective immediately upon infection Specific immunity (adaptive or acquired immunity)

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

Download Presentation

Ch 43- Immune system

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript

Ch 43 immune system

Ch 43- Immune system

Immune system

Immune system

  • Defends body against disease

    • Pathogens – agents of disease (bacteria, viruses, protists)

  • Non specific immunity (innate immunity)

    • All animals & plants have defenses effective immediately upon infection

  • Specific immunity

  • (adaptive or acquired immunity)

    • All vertebrates have immunity after exposure to pathogens (slower response).

1 non specific immunity

1. Non-specific Immunity

  • 1st line of defense: barrier

  • Skin, mucous membrane, secretions

  • 2nd line of defense: internal defenses

  • Phagocytosis, natural killer cells, antimicrobial proteins, inflammatory response

Invertebrate defenses

Invertebrate defenses

  • 1st barrier – exoskeleton made of chitin

  • Digestive system is protected by a chitin-based barrier and lysozyme, an enzyme that breaks down bacterial cell walls

  • The immune system recognizes bacteria and fungi by structures on their cell walls

Ch 43 immune system



- circulate within hemolymph and carry out phagocytosis, the ingestion and digestion of foreign substances including bacteria

- also secrete antimicrobial peptides that disrupt the plasma membranes of fungi and bacteria




Non specific immunity in vertebrates

Non-specific immunity in Vertebrates

  • Include barrier defenses, phagocytosis, antimicrobial peptides

  • Unique to vertebrates: natural killer cells, interferons, inflammatory response

Barrier defenses

Barrier defenses

  • Skin

  • Mucous membranes

  • Body secretions: saliva ,mucus, tears

  • Low pH in skin & membranes



  • “cell eating” – white blood cells ingest invading pathogens

  • Neutrophils – short lived white blood cells

  • Macrophages – largest phagocytes (from monocytes)

    • Engulfs microbe & fuses with lysosyme to destroy it

    • Found fixed in parts of lymphatic system (spleen, lymph nodes, thymus)

    • Some travel throughout body

  • Eosinophils – attack larger parasites

Ch 43 immune system

  • Phagocytes recognize groups of pathogens with Toll-like receptors (TLRs) that recognize molecular patterns characteristic of certain pathogens

  • This increases efficiency of phagocytes

    • i.e. double stranded RNA (in viruses)

      • Flagellin – protein found in bacteria flagella

Ch 43 immune system

  • Natural killer cells

  • Destroy virus-infected body cells

  • Attack cells membrane, so cell lyses

  • Lymphatic system involved in cellular non-specific defense

  • Lymph nodes hold many macrophages

Ch 43 immune system







Lymphatic vessel


Lymphatic vessel




Masses ofdefensive cells

Antimicrobial proteins

Antimicrobial proteins

  • Proteins involved in attacking microbes or stopping their reproduction

  • Lysozyme- present in tears & saliva, mucous

  • Complement proteins – 20 serum proteins – carry out steps to lyse microbes

  • Interferons – secreted by virus-infected cells, induce neighboring cells to produce chemicals to inhibit viral reproduction

Inflammatory response

Inflammatory response

  • Response to cut or entry of microorganisms

  • Area becomes inflamed, red, swollen

  • Result of chemical signals-

    • From invader

    • Nearby mast cells release histamines – released by body cells in response to injury

    • Histamines dilate capillaries and increase permeability, so fluid & clotting elements leave can enter site

Inflammatory response1

Inflammatory response



Movementof fluid







Redblood cells

Ch 43 immune system

  • Clotting begins

  • Other cells release chemokines, which attract phagocytes to area

  • Phagocytes consume pathogens & debris

  • Pus - a fluid rich in white blood cells, dead pathogens, and cell debris from damaged tissues

2 specific immunity

2. Specific Immunity

  • Specific immune responses to particular microorganisms

  • Found in vertebrates

  • Lymphocytes – type of white blood cells

    • 2 types:

    • T cells – mature in thymus

    • B cells – mature in bone marrow



  • Substances that can elicit a response from a B or T cell

  • B or T cells have antigen receptors specific for parts of that pathogen – so they can recognize specific antigens

Antigen receptors

Mature B cell

Mature T cell

Recognizing antigens

Recognizing antigens

Ch 43 immune system

  • The specificity of the T & B receptors (and antibodies) is a result of shuffling and recombining several gene segments to produce the protein

  • There are more than 1 million different B cells and 10 million different T cells

  • Due to random arrangment, some receptors are specific for epitopes on organism’s own molecules, so B & T cells must be tested for self- reactivity.

Ch 43 immune system

Ch 43 immune system

  • B cells:

  • Mature in bone marrow

  • Produce antibodies

  • Receptors bind to intact antigens

  • T cells:

  • Mature in thymus

  • Do not produce antibodies

  • Receptors bind to antigens displayed by antigen-presenting cells (APCs) on their MHCs


Activated by cytokines, from helper T cells

Ch 43 immune system

  • MHC – major histocompatability complex – cell surface glycoproteins that differ among individuals

    - aid in recognition of “self”

    - Class I – found on nearly all body cells

    - can present fragments of proteins made by infecting microbes to cytotoxic T cells

    - Class II – made by some cells of immune system

    - macrophages & B cells

    - molecules collect remnants of microbes and present them to helper T cells

Clonal selection

Clonal selection

  • Activation occurs when antigen binds to B or T cell.

  • Clones formed in clonal selection – two types produced:

    • Effector cells – fight the antigen

    • Memory cells – have receptors for same antigen, so allow quick response to subsequent infection




  • Primary response- when body first exposed to antigen and lymphocyte is activated

  • Secondary response – when same antigen is encountered later, faster more efficient response due to memory cells

Ch 43 immune system

Primary immune responseto antigen A producesantibodies to A.

Secondary immune response toantigen A produces antibodies to A;primary immune response to antigenB produces antibodies to B.



Antibodiesto A

Antibody concentration(arbitrary units)

Antibodiesto B













Exposure to antigens A and B

Exposureto antigen A

Time (days)

Cell mediated immunity

Cell- mediated immunity

  • Activation & clonal selection of cytotoxic T- cells

  • Macrophages engulf antigens, process them internally, then display parts of them on their surface together with some of their own proteins. This sensitizes the T cells to recognize these antigens.

Ch 43 immune system

  • T-cells are trained in thymus

  • T- cells are chosen that have correct receptors to recognize MHC molecules

  • T- cells that can recognize MHC molecules complexed with foreign peptide are allowed to pass out of thymus

Ch 43 immune system

  • Cytotoxic T cells (Killer T cells) bind to class 1 MHC molecules, display fragments on surface of body cells. Destroy infected cells.

  • Helper T-cells: secrete cytokines in response to interaction with class 2 MHC molecules – stimulate & activate both cytotoxic T cells & B cells

  • Memory T cells – recognize & respond to antigen once it has already been encountered.


Humoral response

Humoral response

  • Activation & clonal selection of effector B cells

  • Fight pathogens in body fluids

  • Activated B cells produce plasma & memory cells

  • Plasma cells –(effector cells) produce antibodies

  • Memory cells – for secondary response

Ch 43 immune system

  • Antibodies – soluble proteins secreted by B cells during an immune response

  • Antibodies destroy antigens through:

    • Neutralization: bind & block activity of antigen

    • Lysis: caused by activation of complement system- form a hole in membrane of pathogen

    • Agglutination: clumping of bacteria or viruses

    • Opsonization: results in increased phagocytosis of antigen (attracts macrophages)

Ch 43 immune system

  • Humoral response:


  • Specific immunity


Ch 43 immune system

  • Active immunity – when body is exposed directly to pathogen, body responds

  • (infection, vaccination)

  • Passive immunity – when an individual receives antibodies

  • (to fetus from mother across placenta)

Ch 43 immune system

  • Allergy reaction animation


  • Login