First line of defense
Physical and mechanical barriers that prevent the entry of pathogens into the body.
Second line of defense
Inflammation, a quick and nonspecific response to injury or infection that aims to neutralize and limit the cause of injury, clean the site through phagocytosis, and promote healing.
Neutrophils
Inflammatory cells that neutralize and destroy invading bacteria or microorganisms through phagocytosis.
Monocytes
Inflammatory cells that later become macrophages or dendritic cells and play a role in phagocytosis and alerting other blood cells to help kill pathogens.
Eosinophils
Inflammatory cells involved in allergic reactions.
Lymphocytes
Inflammatory cells that play a role in the adaptive immune response.
Opsonization
The process of coding pathogens with antibodies or complement proteins to enhance phagocytosis.
Complement system
A group of proteins produced by the liver that help in inflammation and phagocytosis through opsonization and other mechanisms.
Chemical mediators of inflammation
Substances such as prostaglandins, histamine, and nitric oxide that play a role in vasodilation, pain, and other aspects of inflammation.
Fever
A systemic response to inflammation characterized by increased body temperature, which can help the body fight off infections.
Wound healing
The process of repairing damaged tissue through clotting, inflammation, proliferation, angiogenesis, and collagen production.
Acute inflammatory response
A rapid and localized response to tissue injury characterized by redness, swelling, and pain.
Chronic inflammatory response
A prolonged and persistent inflammatory process that can lead to chronic inflammatory diseases such as arthritis and tendinitis.
Adaptive immunity
The immune response mediated by B and T cells, which are able to recognize and remember specific antigens.
Humoral immunity
The immune response mediated by antibodies produced by plasma cells in response to antigens.
Cell-mediated immunity
The immune response mediated by cytotoxic T cells, which can kill infected or abnormal cells.
Hypersensitivity
An altered immune response to an antigen that results in disease or damage to the individual, classified into four types.
Opportunistic infections
Infections caused by non-pathogenic microorganisms that become pathogenic in individuals with immune deficiencies.
Primary immune deficiency
Rare congenital disorders that result in immune system defects.
Secondary immune deficiency
Acquired immune deficiencies caused by other conditions such as pregnancy, aging, and stress.
HIV
Human immunodeficiency virus, the virus that attacks and destroys CD4 T cells and can lead to AIDS if left untreated.
AIDS
Acquired immunodeficiency syndrome, the late stage of HIV infection characterized by severe depletion of CD4 T cells and increased susceptibility to infections.
Clinical progression of HIV
The stages of HIV infection, including initial viremia, latency, and the onset of AIDS symptoms.
Clinical manifestation of AIDS
The clinical features associated with AIDS, including a decrease in CD4 count and a weakened immune system.
Opportunistic infections
Infections caused by microorganisms such as protozoa, fungi, bacteria, and viruses that take advantage of a weakened immune system.
Cancer
A disease characterized by the uncontrolled growth and spread of abnormal cells in the body.
Kaposi sarcoma
The most common opportunistic infection associated with HIV/AIDS, characterized by the development of abnormal skin lesions.
Brain lymphoma
An opportunistic infection that affects the brain and is commonly seen in individuals with HIV/AIDS.
Cervical cancer
A type of cancer that affects the cervix and is associated with certain strains of human papillomavirus (HPV).
Fever
A symptom of infection that indicates the immune system is responding to the presence of pathogens.
Pathogenicity
The ability of an infectious agent to cause disease by causing harm to the host.
Opportunism
The phenomenon in which normally benign microorganisms become pathogenic due to a decrease in the host's resistance.
Virulence
The capacity of a pathogen to cause severe disease.
Agent-host interaction
The combination of a pathogen's pathogenicity and the host's defense mechanisms.
Zoonosis
Infections that are harbored in animals and can be transmitted to humans.
Incubation period
The time between exposure to an infectious agent and the onset of symptoms.
Prodomal stage
The stage of infection characterized by non-specific infectious symptoms.
Invasion period
The stage of infection characterized by specific signs and symptoms.
Convalescence
The stage of infection in which the host's immune and inflammatory systems succeed in resolving the infection and promoting recovery.
Pathogenesis of fever and acute phase response
The process by which infection leads to the development of fever and the activation of the acute phase response, involving the release of various cytokines and other immune molecules.
Colonization
The establishment of microorganisms on a body surface or within a host.
Invasion
The process by which microorganisms enter and spread within the host's tissues.
Multiplication
The growth and replication of microorganisms within the host's tissues.
Dissemination
The spread of microorganisms from the initial site of infection to other areas of the body.
Biofilm
A community of microorganisms that adhere to a surface and can resist the immune system and antimicrobial treatments.
Bacterial infections
Infections caused by bacteria, which can be classified based on their shape (cocci, bacilli, spirochetes) and their staining characteristics (gram-positive, gram-negative).
Lipopolysaccharides (LPS)
Toxic components present in the outer membrane of gram-negative bacteria that can activate the immune system and cause inflammation.
Bacteremia
The presence of bacteria in the bloodstream.
Septicemia
A severe infection caused by bacteria that has spread throughout the body via the bloodstream.
Fungal infections
Infections caused by fungi, which can be superficial or opportunistic and often affect individuals with weakened immune systems.
Mycoses
Another term for fungal infections.
Protozoa
Single-celled organisms that can cause parasitic infections in humans.
Helminths
Multicellular parasites, such as worms, that can cause infections in humans.
Vector
An organism, often an insect, that carries and transmits a pathogen to a host.
Viral infections
Infections caused by viruses, which are obligate intracellular microorganisms that can specifically target and infect different types of cells in the body.
Antigenic shifts
Mutations in the genes and antigens of viruses that can lead to the emergence of new variants and strains.
SARS
Severe acute respiratory syndrome, a viral respiratory illness caused by the SARS coronavirus.
MERS
Middle East respiratory syndrome, a viral respiratory illness caused by the MERS coronavirus.
COVID-19
Coronavirus disease 2019, a viral respiratory illness caused by the SARS-CoV-2 coronavirus.
Spike protein
A protein on the surface of the coronavirus that allows it to bind to ACE2 receptors on host cells and facilitate viral entry.
mRNA
Messenger RNA, a type of RNA that carries the genetic information from DNA to the ribosomes for protein synthesis.
General adaptation syndrome (GAS)
A non-specific physiological response to stressors that allows the body to adapt and cope with stress.
Acute stress
Short-term stress that activates the body's fight or flight response.
Chronic stress
Long-term stress that can have negative effects on the body's physiological and psychological well-being.
Alarm phase
The initial phase of the general adaptation syndrome, characterized by the body's recognition and response to a stressor.
Resistance or adaptation phase
The phase of the general adaptation syndrome in which the body adapts to the ongoing stressor and remains on guard.
Exhaustion phase
The final phase of the general adaptation syndrome, characterized by the depletion of the body's resources and increased vulnerability to stress-related illnesses.
Homeostasis
The state of balance and stability within the body's internal environment.
Allostasis
The process of achieving and maintaining homeostasis through adaptive physiological responses to stress.
Physiology of the acute stress response
The body's immediate physiological response to stress, involving both neural (sympathetic) and hormonal (pituitary-adrenal) pathways.
Cortisol
A glucocorticoid hormone produced by the adrenal cortex that plays a key role in the body's response to stress.
Metabolic response
The physiological changes in metabolism that occur in response to stress, including increased mobilization of glucose for energy.
Cardiovascular effects
The effects of stress on the cardiovascular system, including increased heart rate, myocardial contractility, and blood pressure.
Adrenal gland
An endocrine gland located on top of the kidneys that plays a crucial role in the body's response to stress, producing hormones such as epinephrine and cortisol.