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acquired immunity 8 activated lymphocyte
lymphadenopathy, multiple infections, neurologic disease,
and in some cases secondary neoplasms. Opportunistic
infections account for 80% of deaths in AIDS patients.
Prominent among these is pneumonia caused by
Pneumocystis carinii as well as other common pathogens.
AIDS patients also have a high incidence of certain tumors,
especially Kaposi sarcoma, non-Hodgkin lymphoma, and
cervical cancer in women. No effective vaccine has yet
been developed.
Opsonic—promote ingestion and killing by phagocytic cells (IgG)
Block attachment (IgA)
Neutralize toxins
Agglutinate bacteria—may aid in clearing
Render motile organisms nonmotile
Abs only rarely affect metabolism or growth of bacteria (Mycoplasma)
Abs, combining with antigens of the bacterial surface, activate the
complement cascade, thus inducing an inflammatory response and
bringing fresh phagocytes and serum Abs into the site
Abs, combining with antigens of the bacterial surface, activate the
complement cascade, and through the final sequences the membrane
attack complex (MAC) involving C5b-C9 is formed
Antimicrobial Actions of Antibodies
acquired immunity
Protective resistance against an infectious agent generated
as a consequence of infection with a specific microorganism
or as a result of deliberate immunization. Refer also to
primary immune response, secondary immune response,
and adaptive immunity.
acquired immunodeficiency
A decrease in the immune response to immunogenic (antigenic)
challenge as a consequence of numerous diseases or
conditions, including acquired immunodeficiency syndrome
(AIDS), chemotherapy, immunosuppressive drugs such as
corticosteroids, psychological depression, burns, nonsteroidal
antiinflammatory drugs, radiation, Alzheimer’s disease,
celiac disease, sarcoidosis, lymphoproliferative disease,
Waldenström’s macroglobulinemia, multiple myeloma,
aplastic anemia, sickle cell disease, malnutrition, aging,
neoplasia, and diabetes mellitus, among others.
Strain A (i.e. C57BI/6)
Allograft from
strain A mouse
Splenic cells
taken from strain A
mouse
Strain B mouse with tolerance
to strain A allograft
acquired tolerance
Immunologic tolerance induced by the inoculation of a
neonate or fetus in utero with allogeneic cells prior to maturation
of the recipient’s immune response. The inoculated
antigens are accepted as self. Immunologic tolerance to
some soluble antigens may be induced in neonates by low-
dose injections of the antigen or in older animals by larger
doses; the so-called low dose and high dose tolerance,
respectively. Refer also to immunologic tolerance.
acridine orange
A fluorescent substance that binds nonspecifically to RNA
with red fluorescence and to DNA with green fluorescence.
It also interacts with polysaccharides, proteins, and
glycosaminoglycans. It is a nonspecific tissue stain that
identifies increased mitoses and shows greater sensitivity
but less specificity than the Gram stain. It is carcinogenic
and of limited use in routine histology.
ACT-2
A human homolog of murine MIP-1b that chemoattracts
monocytes but prefers activated CD4 + cells to CD8 + cells. T
cells and monocytes are sources of ACT-2.
actin
In immunology, the principal muscle protein that together
with myosin causes muscle contraction and is used in surgical
pathology as a marker for the identification of tumors of
muscle origin. Actin is identified through immunoperoxidase
staining of surgical pathology tissue specimens.
activated dendritic cells
Refer to dendritic cells.
activated leukocyte cell adhesion molecule (ALCAM/CD166)
A member of the immunoglobulin (Ig) gene superfamily. It
is expressed by activated leukocytes and lymphocyte antigen
CD6. The extracellular region of ALCAM contains five Ig-like
domains. The N terminal Ig domain binds specifically to CD6.
ALCAM/CD6 interactions have been implicated in T cell
development and regulation of T cell function. ALCAM may
also play a role in the progression of human melanoma.
activated lymphocyte
A lymphocyte whose cell surface receptors have interacted
with a specific antigen or with a mitogen such as phytohemagglutinin,
concanavalin A, or staphylococcal protein A. The
morphologic appearance of the activated (or stimulated) lymphocyte
is characteristic, and in this form the cells are called
Pregnant
strain B
(i.e. white coat H-2 s )
Acquired immunologic tolerance.
Strain B fetus
Splenic cells
taken from strain A
injected in utero