BHS 329 Unit 4

What is innate immunity

The body’s line of first defense.

Rapid, non-specific, no memory.

What cells are included in innate immunity

Includes neutrophils, macrophages, dendritic cells, NK cells, inflammation

What is adaptive immunity

The body’s specific immune response.

Slower first response (days), specific for each antigen, has memory

What cells are included in adaptive immunity

B cells, T cells, antibodies

What are the main differences between innate and adaptive immunity

Innate: fast, nonspecific, no memory, inflammation

Adaptive: slow, antigen-specific, memory, antibodies and T-cells

What is active immunity?

Your own immune system makes antibodies.

Examples: infection, vaccination

What is passive immunity?

Recieve antibodies from another source

Examples: breast milk (IgA), placenta (IgG)

Immediate but temporary

Why was COVID plasma used?

Plasma from recovered patients contained antibodies that could provide temporary passive immunity

What is plasma?

Liquid portion of blood containing antibodies, proteins, clotting factors, electrolytes, nutrients

What are the risks of plasma transfusions

Allergic reactions, blood incompatibility, infection transmission, variable antibody levels

Which antibody is most common?

IgG

75% of antibodies, crosses placenta, secondary immune response

Which antibody is first produced

IgM (first responder, activates complement)

Which antibody protects mucosal surfaces

IgA in tears, saliva, breast milk, GI tract

Which antibody causes allergies

IgE binds mast cells, histamine release, anaphylaxis

What does IgD do

Activates B cells

Why do we need different antibody classes

Each works best in different tissues or stages of immunity

IgA → mucosa

IgG → blood

IgE → parasites/allergies

IgM → early infection

What is the function of a neutrophil

First immune cell to infection, kills bacteria by phagocytosis, innate immunity

What is the function of dendritic cells?

Best antigen-presenting cell. Links innate → adaptive immunity

NK cell function

Kills virus-infected cells, cancer cells

No antigen specificity

Innate immunity

What is the function of plasma B cells

Produce antibodies, adaptive immunity

What is the function of memory cells

Respond rapidly during second exposure. Provide long-term immunity

What are the function of helper (CD4) T-cells

Coordinate immune response. Activate B cells, Cytotoxic T cells, macrophages

What is the function of cytotoxic (CD8) T cells

Directly kill infected cells

What do B cells do

Produce antibodies (humoral immunity)

What do T cells do

Cell-mediated immunity and destroy infected cells

What do dendritic cells/macrophages do

Eat pathogens → present antigen → activate T cells

What is MHC 1

Found on almost all body cells

Recognized by CD8 cytotoxic T cells

What is MHC II

Found on antigen-presenting cells

Recognized by CD4 helper T cells

What is the primary response

First exposure, slow, mostly IgM

What is the secondary response

Second exposure, much faster, mostly IgG, memory cells are involved.

Why do flu vaccines change every year?

Influenza undergoes frequent antigenic variation (mutation)

Why is measles immunity lifelong

Measles virus changes very little, memory cells recognize it for life

Why can you get multiple colds

Many different cold viruses and antigen variants

What type of hypersensitivity is allergy?

Type I

Which antibody causes allergies

IgE

What cells release histamine

Mast cells, basophils

What does histamine cause

Vasodilation, swelling, itching, bronchoconstriction

What is anaphgylaxis

life-threatening systemic Type I hypersensitivity reaction

How does epinephrine (EpiPen) work>

Opens airways, raises blood pressure, reduces swelling, counteracts histamine

Why doesn’t someone react to poison oak the first time?

Requires prior sensitization

First exposure creates memory T cells

Later exposure causes type IV hypersensitivity

What is the Type I hypersensitivity?

Immediate allergy mediated by IgE antibodies

e.g. Anaphylaxis

What is Type II hypersensitivity

Antibody attacks body cells

e.g. blood transfusion reaction

What is Type III hypersensitivity?

Immune complexes deposit in tissues

e.g. systemic lupus erythematosus (SLE)

What is Type IV hypersensitivity?

T-cell mediated

e.g.poison ivy

Which cells does HIV infect

CD4 helper T cells

Why is HIV difficult to cure?

Without CD4 cells, poor B-cell activation, poor CD8 activation, weak immune response

Virus also establishes latent reservoirs

Low neutrophils

Poor bacterial defense

Low dendritic cells

Poor antigen presentation
Weak adaptive immunity

Low CD8 T cells

Poor viral killing

Low B cells

Few antibodies. Frequent infections

Three major drug classes

Corticosteroids, cytotoxic drugs, biological agents

Why are targeted biologics preferred?

Suppress only abnormal immune pathways instead of the entire immune system

What causes immune amnesia

Measles virus

What does the measles virus do?

Destroy memory B and T cells. Previously acquired immunity is lost

What is the treatment for severe measles virus cases?

Supportive care, sometimes IV immunoglobulin

What is autoimmunity

Immune system attacks itself

What is SLE

autoimmune disease targeting nuclear components (DNA, RNA, proteins). Systemic because every cell contains nuclei.

Why are SLE symptoms so varied

Many organs can be affected: skin, kidneys, joints, brain, blood

Why is RhIg given to Rh-negative mothers

RhIg destroys fetal Rh-positive RBCs before the mother’s immune system recognizes them

prevents formation of anti-Rh antibodies

Protects future pregnancies

What are the main functions of the lymphatic system

Returns tissue fluid to blood, filters pathogens, houses lymphocytes, an initiates immune responses

What is the difference between lymphatic system and circulatory system?

Circulatory: closed loop, pumps blood
Lymphatic: one-way flow, returns lymph to bloodstream