Chapter 4: Immunology

What is immunology?

Protection from infectious disease by the immune system

T lymphocytes

• Cytotoxic T cell: specific cellular antigen destruction (viruses and tumor cells)

• Helper T cell: activation of antigen-specific T cell

• Suppressor cells: inhibit humoral and cell-mediated responses (limit immune response)

B lymphocytes

• Memory cells: efficient, rapid antibody response to antigen recognition

• Plasma cells: secretes antibodies/immunoglobulins

What are peripheral organs where lymphocytes are kept? What is their purpose?

Spleen, lymph nodes, appendix, tonsils

• Serve as maintenance sites and immune responses are often initiated here

What is the difference between the innate and adaptive response?

Innate- nonspecific, 1st line of defense, happens early and fast, includes skin, mucous membranes, inflammation, NK cells, APCs (dendritic cells), WBCs

Adaptive is specific towards a specific antigen, recognize plan and attack, B and T lymphocytes

Active vs Passive immunity

Active: development of antibodies in own body: vaccines or disease acquisition

Passive: through placenta. breast milk, injection of antibodies

Humoral vs Cell-Mediated immunity

Humoral: B lymphocytes recognize antigens, differentiate into plasma cells and secrete antibodies. In the blood and mucous membranes

Cell-mediated: T lymphocytes recognize APCs. Inside cells

Helper T cells vs Cytotoxic T cells

• CD4 helps B cells w/ antibody production and phagocytes destroy contents.

• CD8 kills intracellular microbes

IgA, IgD, IgE

• IgA: passive immunity from breastmilk

• IgD: antigen-binding

• IgE: allergies and inflammation

IgG and IgM

• IgG: GREETS antigens every every time, most abundant and cross placenta

• IgM: MEETS antigens once, memory cells and are first to be produced

MHC 1 vs MHC 2

1. bacterial intracellular infection, activate macrophages, secrete chemokines and cytokines to attract macrophages, promote fusion of lysosomes with vesicles containing bacteria, and stimulate phagocytosis

2. activate B cells to produce antibodies

Why are MHC molecules important?

Differentiate self vs non-self antigens

What are 4 different ways altered immunity can occur?

• Failure of host defense mechanisms: the impaired ability to mount an immune defense

• Hypersensitivity: inappropriate excessive immune responses

• Autoimmunity: inappropriate response to “self”

• Alloimmunity: reactions directed at tissue antigens from other individuals of the same species (graft rejection)

How can host defense failure occur?

1. antigenic variation: multiple variations of antigens, avoiding B/T lymphocyte recognition

2. Viral latency

3. Immunodeficiency

Primary vs Secondary immunodeficiency

Primary: inherited/congenital, mutations, recurrent persistent or unusual infections occur

Secondary: acquired, no cure

What are the most common allergens in children? Adults?

Children- peanuts, tree nuts, milk, eggs, wheat, soy

Adults- peanuts, tree nuts, shellfish, fish

Type 1 hypersensitivity reactions

IgE mediated sensitivities

• Ex: insect things, bees

  Treatment: venom immunotherapy

Type 2 hypersensitivity reactions

Mistaken identity

• Ex: drug reactions, blood transfusion reactions, Graves disease, hemolytic disease of newborn

Results in anemia, thrombocytopenia, and leukopenia

Type 3 hypersensitivity reactions

• Ex: lupus and RA

Type 4 hypersensitivity reactions

T lymphocyte–mediated reactions

• Direct cell mediated toxicity: CD8 cells attack all infected cells with recognized antigens whether harmful or not

• Delayed hypersensitivity reaction: contact dermatitis

• Ex: poison ivy, exposure to TB

Examples of alloimmunity

allograft (body tissues) or autotransfusion (body fluids or plasma)

Treatment of maladaptive immune responses

• anti-inflammatory drugs: corticosteroids

• cytotoxic drugs: methotrexate

• bacterial/fungal drugs:

Factors affecting immune response

• Age: young kids and aging adults

  • decreased immune function, more susceptible to infection, autoimmune and immune disorders, cancer, etc.