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How do you calculate an absolute white blood cell count?

Multiply the total WBC count by the percentage of the specific cell type expressed as a decimal.

A cat has 18,000 WBCs and 70% neutrophils. What is its absolute neutrophil count?

18,000 × 0.70 = 12,600 neutrophils per microliter.

What is the function of MHC I?

Presents mainly intracellular antigen fragments to CD8 cytotoxic T cells.

What is the function of MHC II?

Presents mainly processed extracellular antigen fragments to CD4 helper T cells.

Which T cells recognize antigens presented on MHC I?

CD8 cytotoxic T cells.

Which T cells recognize antigens presented on MHC II?

CD4 helper T cells.

What happens if a macrophage cannot present antigens on MHC II?

CD4 helper T cells cannot properly recognize the processed antigens presented by that macrophage.

How do cytotoxic T cells destroy virus-infected cells?

They recognize viral peptides displayed on MHC I and trigger the infected cell to undergo apoptosis.

Which immune cells recognize abnormal cells with reduced MHC I expression?

Natural killer cells can detect reduced MHC I expression together with other activating signals.

What is the difference between natural killer cells and cytotoxic T cells?

Natural killer cells belong to innate immunity. Cytotoxic T cells belong to adaptive immunity and recognize specific antigens.

Which three cells are professional antigen-presenting cells?

Dendritic cells, macrophages, and B cells.

What is the function of dendritic cells?

They capture, process, and present antigens and are especially effective at activating naive T cells.

What is the function of macrophages?

They engulf and digest pathogens, release cytokines, and present processed antigens to helper T cells.

What is the function of helper T cells?

They coordinate immune responses by releasing signals that help activate other immune cells.

What is the function of plasma cells?

They produce and secrete large quantities of antigen-specific antibodies.

Where do plasma cells come from?

Activated B cells differentiate into antibody-secreting plasma cells.

What is antigenicity?

The ability of a substance to be specifically recognized by antibodies or immune receptors.

What is immunogenicity?

The ability of a substance to stimulate an immune response.

A vaccine stimulates antibody and memory cell production. Which property is demonstrated?

Immunogenicity, because it triggers an immune response rather than simply being recognized.

What is humoral immunity?

Adaptive immunity involving B cells and antibodies that primarily defend against extracellular pathogens and toxins.

What is cell-mediated immunity?

Adaptive immunity involving T cells that help defend against intracellular pathogens and abnormal cells.

Antibodies neutralize bacterial toxins in a dog's bloodstream. Which type of immunity is involved?

Humoral immunity, because antibodies are responsible for the protection.

Why is the primary immune response slower?

Naive lymphocytes must recognize the antigen, become activated, multiply, and differentiate.

Why is the secondary immune response faster and stronger?

Memory cells already recognize the antigen and can respond rapidly when reexposed.

Which antibody class is usually produced first during a primary immune response?

IgM.

Which antibody class often dominates a secondary systemic immune response?

IgG.

What is the function of the antibody variable region?

It recognizes and binds a specific epitope, determining antigen-binding specificity.

What is the function of the antibody constant region?

It determines antibody class and helps determine antibody functions.

What changes when a B cell switches from IgM to IgG?

The heavy-chain constant region changes, resulting in a different antibody class.

What remains unchanged by antibody class switching itself?

The original antigen-binding specificity.

Why can IgM and IgG recognize the same epitope after class switching?

Class switching changes the constant region without directly changing the antigen-binding variable region.

What is neutralization?

Antibodies block toxins or pathogens from attaching to target cells.

What is opsonization?

Antibodies coat pathogens, making them easier for phagocytes to recognize and engulf.

What is natural active immunity?

Immunity developed when natural exposure or infection stimulates an individual's own immune response.

What is artificial active immunity?

Immunity developed when vaccination stimulates an individual's own immune response and memory cells.

What is natural passive immunity?

Temporary protection obtained through natural transfer of maternal antibodies.

What is artificial passive immunity?

Temporary protection obtained through medical administration of preformed antibodies.

What is antibody cross-reactivity?

An antibody recognizes similar or shared epitopes found on different antigens.

How can cross-reactivity cause a false-positive diagnostic result?

Diagnostic antibodies recognize similar epitopes on another pathogen and incorrectly indicate that the target pathogen is present.

Which diagnostic characteristic decreases when cross-reactivity causes more false positives?

Specificity decreases because more individuals without the target condition incorrectly test positive.

What do CD8 cytotoxic T cells do when they recognize an antigen on MHC I?

Destroy the infected cell after recognizing the antigen on MHC I.

Which T cells coordinate immune responses by releasing signals?

CD4 helper T cells, which release signals that coordinate the immune response.

Which immune cells detect and destroy abnormal cells that have reduced MHC I expression?

Natural killer cells, which recognize and destroy abnormal cells.

Which cells secrete large amounts of antibodies after B cell activation?

Plasma cells, which are activated B cells that produce antibodies.

Which antigen-presenting cells activate naive T cells?

Dendritic cells, which capture, process, and present antigens to activate naive T cells.

Which receptor on B cells receives activation signals from helper T cells?

CD40, a receptor on B cells that receives activation signals.

Which signaling molecule on activated helper T cells binds CD40?

CD40L, a signaling molecule on activated helper T cells that binds CD40.

Which type of adaptive immunity relies on B cells and antibodies?

Humoral immunity, which relies on B cells and antibodies for primarily extracellular defense.

Which type of adaptive immunity uses T cells against intracellular pathogens?

Cell-mediated immunity, which uses T cells to defend against intracellular pathogens and abnormal cells.

Which part of an antibody determines which epitope it recognizes?

The variable region, which determines which specific epitope an antibody recognizes.

Which part of an antibody determines its class and helps determine its function?

The constant region, which determines antibody class and helps determine its function.

Which antibody action blocks pathogens or toxins from attaching to host cells?

Neutralization, which blocks toxins or pathogens from attaching to host cells.

Which process tags pathogens so phagocytes can engulf them more easily?

Opsonization, which tags pathogens to make phagocytosis easier.

Which property describes a substance being specifically recognized by antibodies?

Antigenicity, the ability to be specifically recognized by antibodies or immune receptors.

Which property describes a substance that triggers an immune response?

Immunogenicity, the ability to stimulate an immune response.

Which type of immunity results from vaccination?

Artificial active immunity, in which the body produces its own immune response.

Which diagnostic weakness causes healthy individuals to test positive?

Poor specificity, meaning healthy individuals are incorrectly identified as positive.

Which diagnostic weakness causes infected individuals to test negative?

Poor sensitivity, meaning infected individuals are not identified.

What do different antigens share that can cause antibody cross-reactivity?

Shared or similar epitopes, which allow antibodies to recognize different antigens.