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B cell coreceptor 94 B cell lymphoproliferative syndrome (BLS)
loss, fatigue, and large cell lymphoma are referred to as
having undergone Richter transformation, usually leading
to death.
B cell coreceptor
A three-protein complex that consists of CR2, TAPA-1, and
CD19 that associates with the B cell receptor and facilitates
its response to specific antigen. CR2 unites not only with
an activated component of complement but also with CD23.
TAPA-1 is a serpentine membrane protein. The cytoplasmic
tail of CD19 is the mechanism through which the complex
interacts with lyn, a tyrosine kinase. Activation of the coreceptor
by ligand binding leads to the union of phosphatidyl
inositol–3′ kinase with CD19, resulting in activation. This
produces intracellular signals that facilitate B cell receptor
signal transduction.
C3b
CR1
CR2
CD19
lyn
TAPA-1
B cell coreceptor.
CD19
iC3b
PI3 kinase
CR2
CR2
TAPA-1
Complement receptor complexes on the surfaces of B cells include CR1,
C3b, CR2, CR19, iC3B, CR2 (CD21), and TAPA-1. B cell markers used
routinely for immunophenotyping by flow cytometry include CD19,
CD20, and CD21.
B cell corona
The zone of splenic white pulp comprised mainly of B cells.
B cell differentiation and growth factors
T-lymphocyte-derived substances that promote differentiation
of B lymphocytes into antibody-producing cells. They
can facilitate the growth and differentiation of B cells in
vitro. Interleukins 4, 5, and 6 belong in this category of
factors.
B cell growth factor (BCGF)
See interleukins 4, 5, and 6.
B cell growth factor I (BCGF-1)
An earlier term for interleukin-4.
B cell growth factor II (BCGF-2)
An earlier term for interleukin-5.
B cell lymphoma in the gut.
B cell leukemias
These leukemias may be classified as pre-B cell, B cell, or
plasma cell neoplasms. They include Burkitt’s lymphoma,
Hodgkin disease, and chronic lymphocytic leukemia (CLL).
Neoplasms of plasma cells are associated with multiple
myeloma and Waldenström’s macroglobulinemia. Many
of these conditions are associated with hypogammaglobulinemia
and a diminished capacity to form antibodies in
response to the administration of an immunogen. In CLL,
more than 95% of individuals have malignant leukemic
cells that are identifiable as B lymphocytes expressing
surface immunoglobulin. These patients frequently develop
infections and have autoimmune manifestations such as
autoimmune hemolytic anemia. Chronic lymphocytic
leukemia/small lymphocytic lymphoma patients may have
secondary immunodeficiency that affects both B and T
limbs of the immune response. Diminished immunoglobulin
levels are due primarily to diminished synthesis.
B cell lymphoproliferative syndrome (BLS)
A rare complication of immunosuppression in bone marrow
or organ transplant recipients. Epstein–Barr virus appears
to be the etiologic agent. The syndrome occurs in fewer
than 1% of human leukocyte antigen (HLA)-identical bone
marrow recipients and is more likely in those whose anti-
CD3 monoclonal antibodies have been used to treat graftvs.-host
disease. Clinically, it may be either a relatively mild