Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content +++ INTRODUCTION ++ Monocytes in the blood are in transit. They function in the tissues, where they mature into macrophages and participate in: — Inflammation, including granulomatous reactions, atheroma formation, and tissue repair — Immunologic reactions, including delayed hypersensitivity — Reactions to neoplasia and allografts The need for macrophages in tissues also can be met by local proliferation of macrophages, not requiring increased transit of blood monocytes. In normal subjects, a mean of 87% of blood monocytes intensely express CD14 (lipopolysaccharide receptor) but not CD16 (Fc receptor) (CD14++/CD16–), the classical subset, designated MO1. A mean of 4% of blood monocytes have weaker expression of CD14 and strongly express CD16 (CD14+CD16++), the intermediate subset, designated MO2. A third monocyte subset, at a mean of 9% of blood monocytes, have weak expression of CD14 and strong expression of CD16 (CD14low/CD16++), the nonclassical subset, designated MO3. Distinctions among monocyte subsets have been validated by gene expression profiling. Older persons have a striking decrease in the proportion of classical CD14++/CD16– monocytes to intermediate CD14+/CD16++ monocytes compared with younger persons. Disorders rarely produce abnormalities of monocytes alone in the absence of other blood cell abnormalities. +++ NORMAL BLOOD MONOCYTE CONCENTRATION ++ The monocyte count averages 1.0 × 109/L in neonatal life, gradually decreasing to a mean of 0.4 × 109/L in adult life. Monocytosis (in adults) is a count greater than 0.8 × 109/L. Monocytopenia is a count less than 0.2 × 109/L. +++ HEMATOLOGIC DISORDERS ASSOCIATED WITH MONOCYTOSIS ++ See Table 35–1. ++Table Graphic Jump LocationTABLE 35–1DISORDERS ASSOCIATED WITH MONOCYTOSISView Table||Download (.pdf) TABLE 35–1 DISORDERS ASSOCIATED WITH MONOCYTOSIS Hematologic Disorders Myeloid neoplasms Myelodysplastic syndromes Primary myelofibrosis Acute monocytic leukemia Acute myelomonocytic leukemia Acute monocytic leukemia with histiocytic features Acute myeloid dendritic cell leukemia Chronic myelomonocytic leukemia Juvenile myelomonocytic leukemia Chronic myelogenous leukemia (m-BCR–positive type) Polycythemia vera Primary myelofibrosis Chronic neutropenias Drug-induced neutropenia Postagranulocytic recovery Lymphocytic neoplasms Lymphoma Hodgkin lymphoma Myeloma Macroglobulinemia T-cell lymphoma Chronic lymphocytic leukemia Drug-induced pseudolymphoma Immune hemolytic anemia Idiopathic thrombocytopenic purpura Postsplenectomy state Inflammatory and Immune Disorders Connective tissue diseases Rheumatoid arthritis Systemic lupus erythematosus Temporal arteritis Myositis Polyarteritis nodosa Sarcoidosis Infections Mycobacterial infections Subacute bacterial endocarditis Brucellosis Dengue hemorrhagic fever Resolution phase of acute bacterial infections Syphilis Cytomegalovirus infection Varicella-zoster virus Influenza Gastrointestinal Disorders Alcoholic liver disease Inflammatory bowel disease Sprue Nonhematopoietic Malignancies Exogenous Cytokine Administration Myocardial Infarction Cardiac Bypass Surgery Miscellaneous Conditions Tetrachloroethane poisoning Parturition Glucocorticoid administration Depression Thermal injury Marathon running Holoprosencephaly Kawasaki disease Wiskott-Aldrich syndrome Hemodialysis +++ Neoplastic or Clonal Monocytic Proliferations ++ Myelodysplastic syndrome Acute myelogenous leukemia (myelomonocytic or monocytic types) Chronic myelomonocytic leukemia Juvenile myelomonocytic leukemia Unusual type of BCR-ABL (p190)–positive chronic myelogenous leukemia with monocytosis +++ Reactive (Nonclonal) Monocytic Proliferations ++ Neutropenic states: cyclic neutropenia; ... Your MyAccess profile is currently affiliated with '[InstitutionA]' and is in the process of switching affiliations to '[InstitutionB]'. Please click ‘Continue’ to continue the affiliation switch, otherwise click ‘Cancel’ to cancel signing in. Get Free Access Through Your Institution Learn how to see if your library subscribes to McGraw Hill Medical products. Subscribe: Institutional or Individual Sign In Username Error: Please enter User Name Password Error: Please enter Password Forgot Username? Forgot Password? Sign in via OpenAthens Sign in via Shibboleth