Chapter 21: The Immune System

Fill-in-the-blank practice flashcards covering innate defenses, adaptive immunity, humoral and cellular immune mechanisms, antibodies, lymphocyte maturation, and immunopathologies from Chapter 21.

The immune system relies on two intrinsic systems: the innate (nonspecific) defense system and the __________ defense system.

adaptive (specific)

The first line of innate defense consists of external body membranes, specifically the skin and __________.

mucosae

Keratin found in surface barriers is resistant to weak acids and bases, bacterial enzymes, and __________.

toxins

The protective acidic film of the skin that inhibits bacterial growth is known as the __________.

acid mantle

Saliva, respiratory mucus, and lacrimal fluid contain __________, an enzyme that kills many microorganisms.

lysozyme

Antimicrobial peptides produced by epithelial cells that inhibit microbial growth are called __________.

defensins

Macrophages develop from circulating white blood cells called __________.

monocytes

Fixed macrophages that reside permanently in the liver are known as __________ cells.

Kupffer

The process by which complement proteins or antibodies coat a pathogen to facilitate adherence is called __________.

opsonization

In this scanning electron micrograph (4800x), the purple cell extending its cytoplasmic projections to pull rod-shaped bacteria toward it is a __________.

macrophage

During phagocytosis, the vesicle containing an engulfed particle fuses with a lysosome to form a __________.

phagolysosome

Helper T cells trigger the __________, which releases cell-killing free radicals and oxidizing chemicals such as $H_2O_2$ to kill resistant pathogens.

respiratory burst

Nonphagocytic large granular lymphocytes that attack cancer and virus-infected cells lacking 'self' cell-surface receptors are __________ cells.

natural killer (NK)

The four cardinal signs of acute inflammation are redness, heat, swelling, and __________.

pain

Swelling (edema) during inflammation is caused by increased capillary permeability, which leaks protein-rich fluid called __________ into tissues.

exudate

Produced by the liver in response to inflammatory molecules, __________ is a clinical marker used to assess acute infection and inflammation.

C-reactive protein (CRP)

During phagocyte mobilization, the clinging of neutrophils to capillary walls in response to CAMs is termed __________.

margination

The process by which neutrophils flatten and squeeze through capillary walls into tissues is called __________.

diapedesis

The directional migration of neutrophils toward an inflammatory site along a chemical gradient is known as positive __________.

chemotaxis

Virus-infected cells secrete __________ to stimulate neighboring cells to synthesize proteins that block viral replication and degrade viral RNA.

interferons (IFNs)

The immune interferon secreted by lymphocytes that activates macrophages is IFN __________.

gamma

Leukocytes and macrophages exposed to foreign substances release chemicals called __________, which act on the hypothalamus to raise body temperature.

pyrogens

A benefit of moderate fever is that it prompts the liver and spleen to sequester iron and __________, which are essential nutrients for microorganisms.

zinc

Small, incomplete antigens that are not immunogenic on their own but become immunogenic when bound to carrier body proteins are called __________.

haptens

Class I MHC proteins are displayed on virtually all nucleated body cells except __________.

red blood cells (RBCs)

Class II MHC proteins are specifically displayed on the surfaces of __________.

antigen-presenting cells (APCs)

In the human body, the normal ratio of T cells to B cells is __________.

$$3:1$$

The most effective antigen-presenting cells known for activating naive T cells are __________ cells.

dendritic

During thymic selection, __________ selection ensures that T cells are capable of recognizing self-MHC proteins.

positive

Negative selection in the thymus eliminates developing T cells that bind tightly to self-antigens in order to ensure __________.

self-tolerance

Only about __________ percent of developing T cells survive the thymic selection processes.

$$2\%$$

Immunocompetent B and T cells that have not yet encountered their specific antigen are termed __________.

naive

Effector B cells that synthesize and secrete antibody molecules at a rate of roughly 2000 molecules per second are __________ cells.

plasma

During a primary immune response, peak plasma antibody levels are typically reached within __________ days.

$$10$$

Receiving a vaccination containing dead or attenuated pathogens provides __________ acquired active humoral immunity.

artificially

The passage of maternal antibodies to a fetus via the placenta or to an infant through breast milk is an example of __________ acquired passive immunity.

naturally

The first class of antibody released by plasma cells during an immune response is __________.

IgM

Secretory __________ is predominantly found in body secretions such as saliva, tears, intestinal mucus, and colostrum.

IgA

The most abundant antibody in plasma ($75\text{–}85\%$), which can cross the placental barrier, is __________.

IgG

The class of antibody that mediates Type I hypersensitivity reactions and stimulates eosinophil activity against parasitic worms is __________.

IgE

The four defense mechanisms utilized by antibodies can be remembered by the acronym PLAN: Precipitation, Lysis, Agglutination, and __________.

Neutralization

Naive CD4 cells typically differentiate into helper T cells, while naive CD8 cells differentiate into __________ T cells.

cytotoxic

CD8 cells recognize foreign antigens bound specifically to Class __________ MHC proteins.

I

The cytokine released by macrophages that co-stimulates bound T cells to produce IL-2 and synthesize more IL-2 receptors is __________.

interleukin 1 (IL-1)

Activation of CD8 cells to become cytotoxic T cells requires the essential nutrient vitamin __________.

D

Cytotoxic T cells deliver a lethal hit to target cells by releasing perforins and apoptosis-inducing enzymes called __________.

granzymes

An organ transplant conducted between genetically identical twins is categorized as an __________.

isograft

Severe Combined Immunodeficiency (SCID) syndrome is a congenital disorder caused by a genetic defect in the __________ enzyme.

adenosine deaminase (ADA)

Human immunodeficiency virus (HIV) targets and devastates the immune system primarily by destroying __________ cells.

helper T (TH / CD4)

Mismatched blood transfusion reactions belong to Type __________ (cytotoxic) hypersensitivities.

II

Allergic contact dermatitis and the tuberculin skin test are examples of Type __________ (delayed) hypersensitivities.

IV