Harrison's Internal Medicine Chapter 106. Plasma Cell Disorders Plasma Cell Disorders: Introduction The plasma cell disorders are monoclonal neoplasms related to each other by virtue of their development from common progenitors in the B lymphocyte lineage. Multiple myeloma, Waldenström's macroglobulinemia, primary amyloidosis (Chap. 324), and the heavy chain diseases comprise this group and may be designated by a variety of synonyms such as monoclonal gammopathies, paraproteinemias, plasma cell dyscrasias, and dysproteinemias. Mature B lymphocytes destined to produce IgG bear surface immunoglobulin molecules of both M and G heavy chain isotypes with both isotypes having identical idiotypes (variable regions). . | Chapter 106. Plasma Cell Disorders Part 1 Harrison s Internal Medicine Chapter 106. Plasma Cell Disorders Plasma Cell Disorders Introduction The plasma cell disorders are monoclonal neoplasms related to each other by virtue of their development from common progenitors in the B lymphocyte lineage. Multiple myeloma Waldenstrom s macroglobulinemia primary amyloidosis Chap. 324 and the heavy chain diseases comprise this group and may be designated by a variety of synonyms such as monoclonal gammopathies paraproteinemias plasma cell dyscrasias and dysproteinemias. Mature B lymphocytes destined to produce IgG bear surface immunoglobulin molecules of both M and G heavy chain isotypes with both isotypes having identical idiotypes variable regions . Under normal circumstances maturation to antibody-secreting plasma cells is stimulated by exposure to the antigen for which the surface immunoglobulin is specific however in the plasma cell disorders the control over this process is lost. The clinical manifestations of all the plasma cell disorders relate to the expansion of the neoplastic cells to the secretion of cell products immunoglobulin molecules or subunits lymphokines and to some extent to the host s response to the tumor. Normal development of B lymphocytes is discussed in Chap. 308. There are three categories of structural variation among immunoglobulin molecules that form antigenic determinants and these are used to classify immunoglobulins Chap. 308 . Isotypes are those determinants that distinguish among the main classes of antibodies of a given species and are the same in all normal individuals of that species. Therefore isotypic determinants are by definition recognized by antibodies from a distinct species heterologous sera but not by antibodies from the same species homologous sera . There are five heavy chain isotypes M G A D E and two light chain isotypes k a . Allotypes are distinct determinants that reflect regular small differences between individuals of .
