Page 155 - Essential Haematology

Chapter 9 White cells: Lymphocytes / 141

Computed tomography (CT) scanning is valuable not available for biopsy, bone marrow or liver
in determining the presence and extent of deep biopsy, CT or ultrasound guided trucut deep node
node enlargement. Subsequent investigations will biopsy may be needed in an attempt to reach a
’
depend on the diagnosis made and the patient s histological diagnosis. Biopsy of the spleen is not
particular features. In some cases of deep node performed as it may cause rupture requiring

enlargement, where enlarged superficial nodes are splenectomy.

■ Lymphocytes are immunologically recognition of antigen on antigen -

competent white cells that are involved in presenting cells and formation of plasma
antibody production (B cells) and with the cells (which secrete immunoglobulin) or
body ’ s defence against viral infection or memory B cells. SUMMARY
other foreign invasion (T cells). ■ Immunoglobulins include fi ve subclasses

■ They arise from haemopoietic stem cells in or isotypes, IgG, IgA, IgM, IgD and IgG, all
the marrow, T cells being subsequently made up of two heavy chains and two light
processed in the thymus. chains ( κ or λ ).

■ B cells secrete gammaglobulin antibodies ■ Complement is a cascade of plasma

specifi c for individual antigens. proteins that can either lyse cells or coat
T lymphocytes are further subdivided into (opsonise) them so they are
+
+
helper (CD4 ) and cytotoxic (CD8 ) cells. phagocytosed.

They recognise peptides on HLA antigens. ■ Lymphocytosis is usually caused by acute
+
Natural killer cells are cytotoxic CD8 cells or chronic infections or by lymphoid
that kill target cells with low expression of leukaemias or lymphomas.

HLA molecules. ■ Lymphadenopathy may be localized

■ The immune response occurs in the (because of local infection or malignancy)
germinal centre of lymph nodes and or generalized because of infection,
involves B - cell and T - cell proliferation, non - infectious infl ammatory diseases,
somatic mutation, selection of cells by malignancy or drugs.
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