Flashcards in Chapter 14 Infection and Human Immunodeficiency Virus Infection and Chapter 13 Deck (147)
An antigen is a substance that elicits an?
immune response. Most antigens are composed of protein. All of the body's cells have antigens on their surface that are unique to that person and enable the body to recognize itself.
Immunity is classified as?
innate or acquired
Innate immunity is?
present at birth, and its primary role is first-line defense against pathogens. This type of immunity involves a nonspecific response, and neutrophils and monocytes are the primary white blood cells (WBCs) involved. Innate immunity is not antigen specific, so it can respond within minutes to an invading microorganism without prior exposure to that organism.
Acquired immunity is the?
development of immunity, either actively or passively
Active acquired immunity results from the?
invasion of the body by foreign substances such as microorganisms and subsequent development of antibodies and sensitized lymphocytes. With each reinvasion of the microorganisms, the body responds more rapidly and vigorously to fight off the invader. Active acquired immunity may result naturally from a disease or artificially through immunization. Because antibodies are synthesized, immunity takes time to develop but is long lasting.
Passive acquired immunity implies that the host?
-receives antibodies to an antigen rather than synthesizing them
-may take place naturally through transfer of immunoglobulins across placental membrane from mother to fetus
-Artificial passive acquired immunity occurs through injection with gamma globulin (serum antibodies). benefit of this immunity is its immediate effect
-passive immunity is short lived because person does not synthesize antibodies and does not retain memory cells for antigen
Active: Natural and Artificial Immunity
1) Natural: contact with antigen through actual infection (e.g., chickenpox, measles, mumps)
2) Artificial: Immunization with antigen (e.g., vaccines for chickenpox, measles, mumps)
Passive: Natural and Artificial Immunity
1) Natural: Transplacental and colostrum transfer from mother to child (e.g., maternal immunoglobulins passed to baby)
2) Artificial: Injection of serum with antibodies from one person (e.g., injection of hepatitis B immune globulin) to another person who does not have antibodies
Immune globulins produced by lymphocytes in response to antigens
Humoral immunity consists of antibody-mediated immunity. Since antibodies are produced by plasma cells (differentiated B cells) and found in plasma, the term humoral immunity is used. Production of antibodies is an essential component in a humoral immune response. Each of the five classes of immunoglobulins?
(IgG, IgA, IgM, IgG, IgE) have specific characteristics
1) Cells involved
3) Memory cells
1) Cells involved: B lymphocytes
2) Products: Antibodies
3) Memory cells: Present
4) Protection: Bacteria, Viruses (extracellular), Respiratory and GI pathogens
5) Examples: Anaphylactic shock, Atopic diseases, Transfusion reaction, Bacterial infections
1) Cells involved
3) Memory cells
1) Cells involved: T lymphocytes, macrophages
2) Products: Sensitized T cells, cytokines
3) Memory cells: Present
4) Protection: Fungus, Viruses (intracellular), Chronic infectious agents, Tumor cells
5) Examples: Tuberculosis, Fungal infections, Contact dermatitis, Graft rejection, Destruction of cancer cells
Tumor Necrosis Factor (TNF)
- Proinflammatory mediator
- Activates macrophages and granulocytes
- Promotes immune and inflammatory responses
- Kills tumor cells
- Responsible for weight loss associated with chronic inflammation and cancer
Immune responses that are initiated through specific antigen recognition by T cells are termed cell-mediated immunity. Several cell types and factors are involved in cell-mediated immunity. The cell types involved include?
-Cell mediated immunity is of primary importance in?
T cells, macrophages, and NK cells.
Cell-mediated immunity is of primary importance in
(1) immunity against pathogens that survive inside of cells including viruses and some bacteria (e.g., mycobacteria) (2) fungal infections
(3) rejection of transplanted tissues
(4) contact hypersensitivity reactions
(5) tumor immunity
The primary clinical evidence of immunosenescence is the high incidence of?
malignancies in older adults. Older people are also more susceptible to infections (e.g., influenza, pneumonia) from pathogens that they were relatively immunocompetent against earlier in life. Bacterial pneumonia is the leading cause of death from infections in older adults. The antibody response to immunizations (e.g., flu vaccine) in older adults is considerably lower than in younger adults
A decline in immune function and immune response that occurs with aging
Researchers believe immunosenescence accounts for the increase in?
Cancer and infections
-Chronic infectious agents
AIDS: Prevention of transmission in the healthcare setting
-Maintain standard precautions: hand washing/hygiene, protective barriers (gloves, mask, eye shield, gown)
-Do NOT recap needles and syringes
-Clean up spills of blood and body fluids immediately using germicidal solution
-Consider ALL body fluids to be contaminated
-Avoid contaminating the outside of specimen containers during collection
-Cleanse work surface ares with appropriate germicide (1:10 concentration of household bleach is effective)
Human immunodeficiency virus (HIV) is a?
retrovirus that causes immunosuppression. People with HIV are more susceptible to infections that are normally controlled through immune responses.
Transmission of HIV
HIV can be transmitted through contact with infected blood, semen, vaginal secretions, or breast milk. HIV transmission occurs through sexual intercourse with an infected partner; exposure to HIV-infected blood or blood products; and perinatal transmission during pregnancy, at delivery, or through breastfeeding. HIV is not spread casually
-most common mode of transmission is unprotected sexual contact with an HIV-infected partner
-Sexual activity involves contact with semen, vaginal secretions, and/or blood, all of which have lymphocytes that may contain HIV.
-genital lesions from other sexually transmitted infections (e.g., herpes, syphilis) significantly increase likelihood of transmission
Contact With Blood and Blood Products
-HIV can be transmitted from exposure to blood when sharing drug-using paraphernalia
-Needles, syringes, straws, and other equipment may be contaminated with HIV or other blood-borne organisms, and sharing this equipment can result in disease transmission
-Puncture wounds are the most common means of work-related HIV transmission. The risk of infection after a needle-stick exposure to HIV-infected blood is 0.3% to 0.4% (or 3 or 4 out of 1000)
Perinatal Transmission of HIV
Perinatal transmission from an HIV-infected mother to her infant can occur during pregnancy, delivery, or breastfeeding
- On average, 25% of infants born to women with untreated HIV infection are born with HIV. Fortunately, the risk of transmission can be reduced to less than 2% in settings in which pregnant women are routinely tested for HIV infection and, if found to be infected, treated with antiretroviral therapy (ART), a combination of medication used to control and suppress HIV replication.
Everyone who has AIDS has HIV infection. However, not everyone who has HIV has AIDS. The distinction rests with?
The number of CD4+ T cells the patient has and whether any opportunistic infections have occurred.
Pathophysiology of HIV
-HIV is an RNA virus.
-RNA viruses are called retroviruses because they replicate in a “backward” manner (going from RNA to DNA)
-HIV cannot replicate unless it is inside a living cell
-The CD4+ T cell (CD4 cell), a type of lymphocyte, is the target cell for HIV. HIV enters the CD4+ T cell by binding to protein receptors on the outside of the cell (Fig. 14-1). This process is known as fusion
-Once HIV attached and fused with CD4+ T cell, HIV RNA enters CD4+ T cell and triggers release of reverse transcriptase (enzyme transforms HIV RNA into single strand of DNA). This strand copies itself, becoming double-stranded viral DNA
-enzyme, integrase, allows newly formed double-stranded DNA to integrate itself into host's genetic structure. This action has two consequences: (1) because all genetic material is replicated during cell division, all daughter cells are also infected and (2) viral DNA in the genome directs the cell to make new HIV
-Protease enzyme involved in replication process, cleaves newly formed strands of HIV genetic material into smaller pieces
-New HIV virions then formed and released. The CD4+ T cell is then destroyed after the HIV virions are released.
HIV destroys about 1 billion CD4+ T cells every day. For many years the body can produce new CD4+ T cells to replace the destroyed cells. However, over time the ability of HIV to destroy CD4+ T cells exceeds the body's ability to replace the cells. The decline in the CD4+ T cell count impairs immune function. Generally, the immune system remains healthy with more than 500 CD4+ T cells/µL. Immune problems begin to occur when the count drops below?
500 CD4+ T cells/µL and Severe problems develop with fewer than 200 CD4+ T cells/µL
With HIV, a point is eventually reached where so many CD4+ T cells have been destroyed that not enough are left to regulate immune responses. This allows?
opportunistic diseases (infections and cancers that occur in immunosuppressed patients) to develop. Opportunistic diseases are the main cause of disease, disability, and death in patients with HIV infection