Page 362 - Textbook of Pathology, 6th Edition

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SECTION II

Figure 14.4 Granulopoiesis and the cellular compartments of myeloid cells in the bone marrow, blood and tissues.

6. SEGMENTED GRANULOCYTES. The mature poly- and contains no azurophilic granules but may have fine
morphonuclear leucocytes, namely: the neutrophils, eosino- granules which are larger than those in the mature monocyte.
phils and basophils, are described separately below. 3. MONOCYTE. The mature form of monocytic series is
Common surface markers for all stages of myeloid series
of cells are CD33, CD13 and CD15. However, stages from described below, while the transformed stages of these cells
in various tissues (i.e. macrophages) are a part of RE system
myelocytes to mature neutrophils also carry CD11b and discussed in Chapter 4.
CD14. Band forms and mature neutrophils have further CD Monocyte-macrophage series having specialised function
10 and CD16.
of phagocytosis secrete active products such as lysozyme,
neutral proteases, acid hydrolases, components of
Haematology and Lymphoreticular Tissues
Monocyte-Macrophage Series
complement, tranferrin, fibronectin, nucleosides and several
The monocyte-macrophage series of cells, though comprise cytokines (TNF-α, IL-1, IL-8, IL-12, IL-18). They express
a part of myeloid series alongwith other granulocytic series, lineage-specific molecules CD 14, cell surface LPS receptors
but are described separately here in view of different etc.
morphologic stages in their maturation (Fig. 14.4).
1. MONOBLAST. The monoblast is the least mature of the LYMPHOPOIESIS
recognisable cell of monocyte-macrophage series. It is very
similar in appearance to myeloblasts except that it has Sites of Formation and Kinetics
ground-glass cytoplasm with irregular border and may show The lymphocytes and the plasma cells are immunocompetent
phagocytosis as indicated by the presence of engulfed red cells of the body. In man, the bone marrow and the thymus
cells in the cytoplasm. However, differentiation from are the primary lymphopoietic organs where lymphoid stem
myeloblast at times may be difficult even by electron cells undergo spontaneous division independent of antigenic
microscopy and, therefore, it is preferable to call the earliest stimulation. The secondary or reactive lymphoid tissue is
precursor of granulocytic series as myelomonoblast. comprised by the lymph nodes, spleen and gut-associated
2. PROMONOCYTE. The promonocyte is a young mono- lymphoid tissue (GALT). These sites actively produce
cyte, about 20 μm in diameter and possesses a large indented lymphocytes from the germinal centres of lymphoid follicles
nucleus containing a nucleolus. The cytoplasm is basophilic as a response to antigenic stimulation. Lymphocytes pass