Lymphocyte Circulation And Trafficking

The functional anatomy of the lymphoid system is shown in Figure 2. Normal lymphocytes have highly controlled circulation and homing mechanisms known as trafficking. The process starts with the production of lymphoid progenitors in the bone marrow which produces between 1010 and 10" lymphocytes a day (9). Only a fraction of these attain maturity, the remainder undergoing apoptosis at the rate of about 7 million per second. Recirculation from lymphatic system to blood occurs at a rate of about 5 million lymphocytes a second. Production, selection and circulation of

Table 1. WHO revision (1998) of the Revised European-American Lymphoma (REAL)

^Classification (The italics show the original (1994) REAL classification terms used)_

Neoplasms_Classification_

B-cell neoplasmas Precursor B-ccll lymphoblastic leukaemia/lymphoma

Mature B-cell neoplasms

B-cell chronic lymphocytic leukaemia/small lymphocytic lymphoma B-ceil prolymphocyte leukaemia

Lymph op lasmacy tic lymphoma (lymphoplasmacytoid lymphoma) Mantle cell lymphoma

Follicular lymphoma {follicle centre lymphoma) Marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) type

Nodal marginal zone lymphoma with or without monocytoid B-cells

Splenic marginal zone B-cell lymphoma

Hairy cell leukaemia

Diffuse large B-cell lymphoma

Subtypes: mediastinal (thymic), intravascular, primary effusion lymphoma

Burkitt lymphoma Plasmacytoma Plasma ccll myeloma

T-cell neoplasms Precursor T-cell lymphoblastic leukaemia/lymphoma

Mature T-cell and NK-cell neoplasms T-celt pro lymphocytic leukaemia T-cell large granular lymphocytic leukaemia NK-cell leukaemia

Extranodal NK/T-cell lymphoma, nasal-type (angiocentric lymphoma)

Mycosis fungoides Sezary syndrome

Angioimmunoblastic T-cell lymphoma Peripheral T-cell lymphoma (unspecified) Adult T-cell leukaemia/lymphoma (HTLV1+) Systemic anaplastic large cell lymphoma (T- and null-cell types) Primary cutaneous anaplastic large cell lymphoma Subcutaneous panniculitis-like T-cell lymphoma Enteropathy-type intestinal T-cell lymphoma Hepatosplenic y5 T-cell lymphoma

Hodgkin's Lymphoma

(Hodgkin's disease Nodular lymphocyte predominance Hodgkin's lymphoma

Classic Hodgkin's lymphoma

Hodgkin's lymphoma, nodular sclerosis (grades I and II) Classical Hodgkin's lymphoma, lymphocyte-rich Hodgkin's lymphoma, mixed ccllularity Hodgkin's lymphoma, lymphocytic depletion (includes some Hodgkin-like anaplastic large cell lymphoma).

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