Chapter 14-Immunity and Infection

A comprehensive set of vocabulary flashcards covering the immune system, infection processes, major pathogens, immunization, allergies, emerging diseases, and sexually transmitted infections as presented in Chapter 14.

Immune system

The body’s collective defenses—including surface barriers, cells, tissues, and organs—that protect against pathogens and cancer.

Innate immune system

Rapid, non-specific first line of internal defense composed of cells such as neutrophils, macrophages, NK cells, eosinophils, and dendritic cells.

Adaptive immune system

Slower, highly specific defense that uses B and T lymphocytes and forms immunological memory.

Physical barriers

External defenses such as skin, mucous membranes, and cilia that block pathogen entry.

Skin

Largest physical barrier; a tough outer layer that prevents pathogen invasion and secretes antimicrobial chemicals.

Mucous membranes

Moist linings of body passages that trap pathogens in sticky mucus.

Cilia

Hair-like projections in the respiratory tract that move mucus and trapped microbes out of airways.

Neutrophils

Most common white blood cells; phagocytic cells of the innate system that ingest bacteria.

Eosinophils

White blood cells that combat parasites and contribute to allergic reactions.

Macrophages

Large phagocytes that engulf pathogens and release signals to activate other immune cells.

Natural killer (NK) cells

Innate lymphocytes that destroy virus-infected and cancer cells without prior exposure.

Dendritic cells

Antigen-presenting cells that start the adaptive response by activating T cells.

Lymphocytes

White blood cells of the adaptive system, including B cells and T cells.

B cells

Lymphocytes that mature into plasma cells and secrete antibodies.

Plasma cells

Activated B cells specialized in producing and releasing large quantities of antibodies.

T cells

Lymphocytes that differentiate into helper, killer, or suppressor subsets to coordinate immunity.

Helper T cells

T cells that coordinate immune responses by releasing cytokines and activating B and killer T cells.

Killer (cytotoxic) T cells

T cells that directly destroy infected or cancerous cells.

Suppressor (regulatory) T cells

T cells that dampen immune activity to prevent overreaction.

Antigen

Any substance (often part of a pathogen) that triggers an immune response.

Antibody

Y-shaped protein produced by plasma cells that binds specifically to an antigen to neutralize it.

Inflammatory response

Innate reaction where blood vessels dilate, fluid and immune cells enter tissue, often producing redness, heat, swelling, pain, and pus.

Cytokines

Chemical messengers released by immune cells to regulate immunity, inflammation, and hematopoiesis.

Memory cells

Long-lived B or T cells that enable a rapid, strong response upon re-exposure to a specific antigen.

Immunity

Protection against a specific pathogen due to memory lymphocytes formed after infection or vaccination.

Lymphatic system

Network of vessels, lymph nodes, and organs (e.g., spleen) that drains fluid and houses immune cells.

Spleen

Organ that filters blood, removes old red cells, and helps mount immune responses.

Lymph nodes

Small organs along lymph vessels where immune cells collect, filter lymph, and fight infection.

Immunization

Process of inducing immunity by exposure to a vaccine containing antigenic material.

Vaccine

Preparation of antigens that primes the adaptive immune system to provide future protection.

Attenuated vaccine

Vaccine containing weakened live organisms that replicate minimally but stimulate strong immunity.

Inactivated (killed) vaccine

Vaccine made of pathogens that have been killed; cannot replicate but still elicit immunity.

mRNA vaccine

Vaccine that delivers messenger RNA coding for an antigen so host cells produce the protein and trigger immunity.

Vaccine efficacy

The ability of a vaccine to prevent disease in a vaccinated population under ideal conditions.

Allergy

Hypersensitive immune response to a normally harmless substance (allergen).

Allergen

Substance (e.g., pollen, dander, food) that provokes an allergic reaction.

Histamine

Inflammatory chemical released during allergic reactions causing itching, swelling, and mucus production.

Anaphylaxis

Severe, life-threatening allergic reaction with airway swelling, low blood pressure, and shock; treated with epinephrine.

Immunotherapy (allergy)

Treatment that gradually desensitizes the immune system to specific allergens.

Incubation period

Time between pathogen entry and appearance of first symptoms; a person may be contagious.

Prodromal period

Early phase of illness when vague symptoms begin and contagion continues.

Chain of infection

Six links—pathogen, reservoir, portal of exit, transmission, portal of entry, new host—describing how disease spreads.

Pathogen

Any microorganism or agent capable of causing disease.

Reservoir

Natural habitat in which a pathogen lives, grows, and multiplies.

Portal of exit

Route by which a pathogen leaves its reservoir (e.g., respiratory secretions).

Vector

Living carrier, such as a mosquito or tick, that transmits a pathogen between hosts.

Portal of entry

Site where a pathogen enters a new host (e.g., skin break, inhalation, ingestion).

Epidemic

Rapidly spreading disease with occurrence higher than expected in a region.

Pandemic

Epidemic that has spread across countries or continents, affecting a large population.

Endemic disease

Disease that is consistently present in a particular geographic area or population.

Bacteria

Microscopic single-celled organisms; some cause diseases like pneumonia, strep throat, and TB.

Antibiotic

Drug that kills bacteria or inhibits their growth by targeting cell walls, protein synthesis, or DNA replication.

Antibiotic resistance

Ability of bacteria to withstand the effects of antibiotics, often due to misuse or overuse of these drugs.

Virus

Tiny infectious agent consisting of genetic material inside a protein coat that replicates only inside host cells.

Antiviral drug

Medication that inhibits viral replication or entry into cells, used for infections like HIV or influenza.

Fungus

Single- or multicelled organism reproduced by spores; causes infections like athlete’s foot and yeast infections.

Protozoa

Microscopic single-celled organisms responsible for diseases such as malaria and giardiasis.

Parasitic worm

Large multicellular organism that lives in or on a host, e.g., tapeworm, hookworm, pinworm.

Prion

Infectious misfolded protein (e.g., PrPSc) that causes neurodegenerative diseases like Creutzfeldt-Jakob disease.

Emerging infectious disease

New or rapidly increasing infection, such as Zika or Ebola, fueled by factors like drug resistance and climate change.

Autoimmune disease

Condition in which the immune system mistakenly attacks the body’s own tissues.

HIV (Human Immunodeficiency Virus)

Retrovirus that destroys CD4 T cells, weakening immunity and leading to AIDS if untreated.

AIDS (Acquired Immunodeficiency Syndrome)

Advanced HIV stage marked by CD4 depletion and opportunistic infections or cancers.

CD4 T cell

Helper T lymphocyte targeted and depleted by HIV; its count gauges HIV disease progression.

Opportunistic infection

Illness caused by organisms that take advantage of weakened immunity, common in AIDS (e.g., Pneumocystis pneumonia).

Antiretroviral therapy (ART)

Combination of drugs that suppress HIV replication and restore immune function.

Postexposure prophylaxis (PEP)

Short course of antiretroviral drugs taken after potential HIV exposure to prevent infection.

Preexposure prophylaxis (PrEP)

Daily medication for people at high risk that greatly reduces chances of acquiring HIV.

Chlamydia

Most prevalent bacterial STI in the U.S., caused by Chlamydia trachomatis; treatable with antibiotics.

Gonorrhea

Bacterial STI caused by Neisseria gonorrhoeae that infects mucous membranes; treated with ceftriaxone.

Pelvic inflammatory disease (PID)

Serious infection of female reproductive organs, often from untreated chlamydia or gonorrhea, leading to infertility.

Human papillomavirus (HPV)

Common viral STI that can cause genital warts and cancers; prevented by vaccination.

Genital herpes

Recurring viral STI caused by HSV-1 or HSV-2, characterized by painful genital lesions; managed with antivirals.

Hepatitis B virus (HBV)

Virus causing liver inflammation; transmitted via blood and body fluids; preventable by vaccine.

Hepatitis A virus (HAV)

Virus spread by fecal–oral route or anal sex; causes acute liver inflammation; vaccine available.

Hepatitis C virus (HCV)

Blood-borne virus often linked to high-risk sexual encounters and injection drug use; chronic infection can damage liver.

Syphilis

Bacterial STI caused by Treponema pallidum with primary, secondary, and tertiary stages; curable with antibiotics.

Trichomoniasis

Common non-viral STI caused by Trichomonas vaginalis; increases HIV risk; treatable with medication.

Bacterial vaginosis (BV)

Imbalance of vaginal bacteria leading to abnormal discharge and odor.

Pubic lice (crabs)

Parasitic insects that infest pubic hair and cause intense itching.

Scabies

Contagious skin infestation by mites that burrow and cause severe itching.