284 The Lymphocyte and Lymphocytic Tissue 



RETICULUM CELL FORMATION OF PLASMA CELLS 



The major structural changes in the transformation of the reticulum cell 

 to the (reticular) plasmablast are noted in the cytoplasm (Fig. 19-17, upper 

 right). The customarily pale cytoplasm of the inactive reticulum cell becomes 

 more basophilic at first near the enlarging cytocentric region and then gradu- 

 ally throughout the entire cell body. The cytoplasmic organelles, which do 

 not stain with ordinary blood stains, show a beginning tendency to aggregate 

 in the region of the cytocentrum which emerges as an indistinct and paler 

 area (hot) in close association with the eccentrically placed nucleus. Azuro- 

 philic granules are exceedingly rare. Evidence of peripheral cytoplasmic dis- 

 solution is commonplace. The round or oval eccentrically placed nucleus 

 has a thin nuclear membrane and a chromatin pattern of fine chromatin 

 strands arranged in an irregular network with distinct pink or yellow 

 parachromatin interstices. The nuclear pattern closely resembles that of 

 the inactive reticulum (ell nucleus (Fig. 19-1) but has thicker chromatin 

 strands; none or from one to six blue nucleoli may be present. 



An intermediate stage, the proplasmacyte, intervenes between the reticular 

 plasmablast and the mature plasma cell. The proplasmacyte (Fig. 19-17, left 

 and top center) has abundant cytoplasm but usually less than the plasma- 

 blast. With shrinkage of the cytoplasm, its basophilia becomes more prom- 

 inent. Aggregation of cytoplasmic organelles in the region of the cytocentrum 

 can result in a clearer perinuclear area (hof) than in the plasmablast. 

 Peripheral cytoplasmic dissolution (cytoplasmic shedding) may still be prom- 

 inent. The round or oval nucleus remains small and eccentric. The nuclear 

 membrane is thickening. The chromatin pattern shows coarsening and 

 thickening of the reticular network; however, irregular interstices of 

 parachromatin are still distinct. One or two nucleoli may still be visible al- 

 though they may be masked. 



With the transformation to the adult or Marschalko type plasma cell com- 

 pleted, the cytoplasmic -nuclear ratio still favors the cytoplasm in many cells, 

 although the cytoplasm is less abundant than in the proplasmacyte. Typically 

 the deep-blue cytoplasm has a large, pale-staining perinuclear area, the hof. 

 Peripheral cytoplasmic dissolution may persist but is less prominent. The 

 eccentric nucleus possesses a thick nuclear membrane. The chromatin shows 

 further condensation. The coarse chromatin masses are arranged in irregular 

 clumps and tend to pyknosis. The parachromatin is small in amount but dis- 

 tinct in the few remaining interstices of the chromatin until pyknosis super- 

 venes. Nucleoli are no longer visible. 



Nonmalignant variations of the plasma cell comprise: nuclear budding, 

 orderly binucleation or multinuc leation, vac notation, and various types of 



