Additional Notes

Immunoglobulin Classes (NCLEX & Pathophysiology Breakdown)

Think of the antibodies as having five jobs. A favorite nursing mnemonic is:

GAMED

• G = IgG

• A = IgA

• M = IgM

• E = IgE

• D = IgD

IgG – "Great, Goes through placenta"

Major Functions

• Most abundant antibody in blood (~75%)

• Provides long-term immunity

• Neutralizes toxins and viruses

• Activates complement

• Promotes phagocytosis

Special Feature

⭐ Only antibody that crosses the placenta

Location

• Blood

• Tissue fluids

Clinical Significance

• Provides passive immunity to fetus

• Elevated after vaccination or past infection

Examples

• Maternal antibodies protecting newborn

• Immunity after chickenpox vaccine

NCLEX Memory Trick

G = Gestation
→ IgG Goes through the placenta

IgA – "A for Areas exposed to outside"

Major Functions

• Protects mucosal surfaces

• Prevents microorganisms from attaching to tissues

Location

Secretions:

• Tears

• Saliva

• Breast milk

• Respiratory tract

• GI tract

• Genitourinary tract

Special Feature

⭐ Main antibody in breast milk

Clinical Significance

• Provides passive immunity to infants

• First defense against respiratory and GI infections

Examples

• Breastfeeding transfers IgA to newborn

• Saliva contains IgA

NCLEX Memory Trick

A = Areas exposed to air
(secretions)

IgM – "M for Massive and Makes first response"

Major Functions

• First antibody produced after exposure

• Activates complement

• Excellent agglutination (clumping)

Location

• Bloodstream

Special Feature

⭐ First responder antibody

Clinical Significance

High IgM = recent or acute infection

Examples

Early hepatitis infection:

• ↑ IgM = current infection

• ↑ IgG = previous infection

NCLEX Memory Trick

M = Massive and Made first

IgE – "E = Allergy and Emergency"

Major Functions

• Allergic reactions

• Anaphylaxis

• Defense against parasites

Location

Bound to:

• Mast cells

• Basophils

When Activated

Releases:

• Histamine

• Leukotrienes

Result:

• Bronchoconstriction

• Vasodilation

• Increased capillary permeability

Clinical Examples

• Asthma

• Allergic rhinitis

• Hives

• Anaphylaxis

• Parasitic infections

NCLEX Memory Trick

E = Emergency
(anaphylaxis)

IgD – "D = Don't know"

Major Functions

• Found on surface of B lymphocytes

• Helps initiate B-cell activation

Location

• B-cell membranes

Clinical Significance

• Least understood

• Very small amount in serum

NCLEX Memory Trick

D = Don't know much about it

Quick Comparison Table

NCLEX High-Yield Associations

Self vs. Non-Self Recognition (NCLEX & Pathophysiology)

One of the most important functions of the immune system is its ability to distinguish "self" (your own body's cells) from "non-self" (foreign substances that may be harmful).

What is "Self"?

Self = the body's own cells and tissues

These include:

• Red blood cells

• Skin cells

• Muscle cells

• Liver cells

• Normal proteins produced by the body

The immune system recognizes these as normal and does not attack them.

Example

Your immune system normally does not attack your kidneys or lungs because they are identified as "self."

What is "Non-Self"?

Non-self = anything foreign to the body

Examples include:

• Bacteria

• Viruses

• Fungi

• Parasites

• Toxins

• Cancer cells

• Transplanted organs

• Foreign proteins (allergens)

The immune system identifies these substances as threats and mounts an immune response.

Example

When influenza virus enters the body:

Virus → recognized as non-self

↓

Immune system activated

↓

Antibodies and T cells attack the virus

↓

Infection eliminated

How Does the Body Recognize Self?

Every cell has markers on its surface called:

Major Histocompatibility Complex (MHC)

Think of MHC molecules as cellular ID badges.

MHC Class I

Present on almost all nucleated cells

Signals:

Recognized by:

• Cytotoxic T cells (CD8)

MHC Class II

Present on antigen-presenting cells:

• Macrophages

• Dendritic cells

• B lymphocytes

Function:

• Present foreign antigens to helper T cells (CD4)

What Happens When the Immune System Sees Non-Self?

Example: Bacteria

Foreign antigen enters body

↓

Macrophage engulfs bacteria

↓

Antigen displayed on MHC II

↓

Helper T cells activated

↓

B cells activated

↓

Antibodies produced

↓

Pathogen destroyed

Immune Tolerance

The immune system learns to tolerate self-antigens and avoid attacking the body's own tissues.

This is called:

Self-Tolerance

Central Tolerance

Occurs in:

• Thymus (T cells)

• Bone marrow (B cells)

Self-reactive cells are destroyed before entering circulation.

Peripheral Tolerance

Controls any self-reactive cells that escape central tolerance.

What Happens When Self-Tolerance Fails?

The body attacks itself, causing:

Autoimmune Disease

Examples:

Example: Type 1 Diabetes

Pancreatic beta cells

↓

Mistakenly recognized as non-self

↓

Destroyed by immune system

↓

Insulin deficiency

↓

Hyperglycemia

Transplant Rejection

The body sees donor tissue as non-self.

Transplanted kidney

↓

Foreign antigens recognized

↓

T cells activated

↓

Attack donor tissue

↓

Rejection

Immunosuppressant drugs are given to prevent this response.

Cancer and Self vs. Non-Self

Cancer cells arise from self cells but may develop abnormal antigens.

Normally:

Abnormal cell

↓

Recognized by cytotoxic T cells and NK cells

↓

Destroyed

Sometimes cancer cells evade immune recognition and continue growing.

Blood Transfusion Reactions

Incorrect blood type

↓

Foreign RBC antigens recognized as non-self

↓

Antibodies attack donor RBCs

↓

Hemolysis

↓

Potentially fatal reaction

Hypersensitivity and Non-Self

Examples of harmless substances recognized as threats:

• Pollen

• Peanuts

• Latex

• Bee venom

Allergen

↓

IgE activation

↓

Histamine release

↓

Allergic response

↓

Anaphylaxis (severe cases)

Flowchart: Normal Immune Recognition

Foreign Antigen

↓

Macrophage Engulfs Antigen

↓

Antigen Presentation (MHC II)

↓

Helper T Cell Activation (CD4)

↓

B Cell Activation

↓

Plasma Cell Formation

↓

Antibody Production

↓

Pathogen Destruction

Flowchart: Autoimmune Disease

Self Antigen

↓

Loss of Self-Tolerance

↓

Immune System Mistakenly Activated

↓

Inflammation

↓

Tissue Damage

↓

Disease

NCLEX High-Yield Table

NCLEX Pearls ⭐

Self = "Leave me alone"

Non-self = "Attack me"

Autoimmune disease = Loss of self-tolerance

Transplant rejection = Response against non-self tissue

Allergies = Overreaction to harmless non-self substances

Cancer = Altered self that escapes immune surveillance