Pathology - L1 - Immunologic Diseases Flashcards
antigen
any substance able to induce a specific immune response
B-lymphocyte functions?
neutralizes microbes, phagocytosis, complement activation
where are B-cells found?
in lymphoid follicles of lymph nodes, bone marrow, and extranodal lymphatic tissue (i.e. tonsils, appendix, Peyer’s patch)
types of T lymphocytes?
helper, cytotoxic, regulatory
helper T-cells functions?
activation of mac’s, in inflamm, activation (proliferation & differentiation) of T & B lymphocytes
Cytotoxic T lymphocyte function?
killing of infected cell or cells harboring microbes
regulatory T lymphocyte function?
suppression of immune response
where are 60-70% of circulating lymphocytes found?
in thymus and paracortical areas of lymph nodes.
60% of lymphocytes have what ?
CD4+ marker; so they are T-helper cells
T-helper cells regulate T and B cell rxns by secretion of _____.
cytokines
30% of circulating lymphocytes have ____. What cells are these?
CD8+ marker; = cytotoxic T-cells (kill cells harboring microbes).
To respond, T cells must have what?
the antigen presented by antigen-presenting cells (APC).
APCs express what molecules?
major histocompatibility molecules (MHC)
T-helper lymphocytes recognized antigens expressed on ____ molecules, whereas cytotoxic lymphocytes recognized antigens expressed on ____ molecules.
class II MHC; class I MHC
antibody-dependent cell-mediated cytotoxicity (ADCC)
- mechanism of cell-mediated immune defense whereby an effector cell of the immune system actively lyses a target cell, whose membrane-surface antigens have been bound by specific antibodies.
- one of the mechanisms through which antibodies, as part of the humoral immune response, can act to limit and contain infection.
- Classical ADCC is mediated by natural killer (NK) cells; macrophages, neutrophils and eosinophils can also mediate ADCC.
- ADCC is part of the adaptive immune response due to its dependence on a prior antibody response.
natural killer cells make what % of blood lymphocytes?
10-15%
Natural killer cells ?
- have no T-cell markers or Ab production
- lyse tumor cells or infected cells w/o previous sensitization
- 1st line of defense against some tumors & viruses
- also can lead to AB-dependent cell-mediated cytotoxicity (ADCC)
function of macrophages?
1) required to process and “present” antigens to lymphocytes;
2) effectors of cell-mediated immunity; produce cytokines influencing growth and function of lymphocytes, inflammation, fibroblast proliferation, and collagen deposition;
3) Phagocytic in response to T-cell activation or opsonization.
members of the macrophage family, although weakly phagocytic?
dendritic cells (in lymphoid tissue); Langerhans cell (in epidermis, oral mucosa)
- important for presenting antigens
- also produce anti-viral cytokines
Ag-Ab activates what…?
9 sequential components aka complement
Complement activates ?
- anaphylaxis (i.e. c3a, c5a)
- chemotaxis (c5a)
- opsoninization (c3b)
- lysis of cells (MAC)
what are cytokines of innate immunity?
intercellular mediators produced in response to microbes and other stimuli and mediate inflammation and anti-viral defense (TNF, IL-1, type 1 IFNs)
functions of cytokines of adaptive immunity?
promote lymphocyte proliferation and differentiation and to activate effector cells (IL-2, IFN-y)
____ stimulates hematopoiesis (colony stimulating factors).
cytokines
innate immunity?
defense mechanisms that are present before infection (i.e. epidermis, phagocytic cells, dendritic cells, NK cells)
adaptive immunity?
- lymphocytes and their products
- humoral vs cell-mediated
humoral immunity?
- associated w/ AB production\
- B lymphocytes and ABs play predominant role
- AB (IgA, IgE, IgG, IgM) act on Ags, resulting in neutralization, lysis, phagocytosis.
cell-mediated immunity?
- cellular neutralization of Ags
- predominant role is played by T-lymphocytes
- Ags are destroyed by lymphocytes, macrophages, etc directly or via cytokines
X-Linked Agammaglobulinemia?
aka Bruton Disease
- failure of pre-B cells to differentiate into B cells
- Ig molecules are not assembled due to failure of light chain production
Clinical features of X-liked Agammaglobulinemia?
- absent or decreased #’s of B cells
- depressed serum levels of all Ig classes
- normal T cell-mediated
- germinal centers (composed mostly of B cells) reduced in size
- recurrent bacterial (pharyngitis, sinusitis, pneumonia) and certain viral infections (enteroviruses)
tx of X-linked Agammaglobulinemia?
replacement therapy w/ human Ig
DiGeorge Syndrome?
- failure of development of 3rd and 4th phraryngeal arches
- absence of thymus, as well as parathyroids
- facial structures will also be underdeveloped
Severe combined immunodeficiency?
- X-linked, associated w/ failure in lymphocyte (esp T-lymphocyte) development
- autosomal recessive form associated w/ deficiency of adenosine deaminase
Isolated IgA deficiency?
typically asymptomatic; compromised mucosal defenses; respiratory, GI, urogenital infections
Complement deficiency?
- angioedema–repaid swelling under dermis
- causes:
1. allergy
2. complement deficency
HIV primarily targets what?
the immune system and CNS
how is HIV transmitted?
sexual contact, parenteral exposure to blood, maternal/fetal
what is the target cell of HIV?
cells w/ CD4 receptors (primarily T-helper lymphocyte)
Viral RNA is permanently integrated into host DNA via… ?
reverse transcription
What is the half-life of HIV?
half-life of 2 days; rapid turnover of HIV
what are the 3 things HIV virus can do?
- remain silent
- cause cell death
- disrupt normal cell function
what is the clinical course of HIV infection?
- acute, self-limited response (similar to infectious mononucleosis)
- 8-10 year asymptomatic stage
- symptomatic stage (AIDS-related complex)
AIDS?
- endpoint of HIV deficiency
- 5 yrs after infection- 18% have AIDS
- 13 yrs after infection - 65% have AIDS, 20% have symptoms, & 15% have no symptoms
AIDS-related complex (ARC) clinical features?
- fever, wt loss, diarrhea, candidiasis, herpes zoster, hairy, leukoplakia
- increased infections: cytomegalovirus, herpes simplex, toxoplasmosis
- pulmonary - pneumocystis carinii oneumonia (presenting sign in 50%)
- AIDS-dementia complex
Type 1 hypersensitivity
allergy/anaphylaxis; IgE mediated
- IgE binds to mast cells, releasing HISTAMINE and other vasoactive amines
Type II hypersensitivity
antibody dependent
- complement dependent (transfusion rxns, erythroblastosis fetalis)
- Ab-dependent cell-mediated cytotoxicity (ADCC)
- Ab-mediated cellular dysfunction (myasthenia gravis, Grave’s disease)
Type III hypersensitivity
- immune complex-mediated (SERUM SICKNESS, glomerulonephritis)
- Ag + Ab + Complement - Recruitment of neutrophils, resulting in tissue destruction
Type IV Hypersensitivty
cell-mediated
- delayed type - TUBERCULIN RXN, poison ivy, contact rxns) T- cells & mac’s; chronic rxns may result in granulomatous inflamm
- T- cell mediated cytotoxicity - type I diabetes - tissue is destroyed by cytotoxic (CD8+) T cells
