Mast cells can be
found on your slide 33 which is a smear of connective tissue stained to help you identify
the mast cells. They are seen by their granules. The relatively large secretory
granules contain histamine which is released after an allergic reaction. How is
histamine triggered and what does it do?
Slide 13 is another connective tissue preparation designed to visualize the macrophages
in connective tissue. These have been exposed to trypan blue, while living and the
macrophages have brought in the dye by phagocytosis, allowing them to be identified.
Nuclei are stained light pink, in this preparation.
PLASMA CELLS See figures above and below.
Plasma Cells and Macrophages
The inner regions of the lymph node slide (slide 34) called the medulla, is filled with connective tissue that contains numerous macrophages (M), eosinophils (E) and plasma cells (P). The macrophages can be identified by their content of large granules. The eosinophils have pale or bright red granules and a lobed nucleus. Plasma cells can be identified by their ovoid shape, nucleus that is off-center, and nuclear chromatin pattern which looks like a "cartwheel". Sometimes there is a pale area like a half moon near the nucleus. This is the Golgi complex. What is the function of a plasma cell?
One of the types of white blood cells, called an eosinophils is found in loose connective tissue and may increase in certain types of inflammatory responses. What types of inflammatory responses would you expect to bring more eosinophils? These cells are distinguished by their bright red granules and their multilobed nuclei. You can see them in your intestine or lymph node slides. Note that in this slide there are numerous eosinophils in the connective tissues under the epithelium. However, two more cells with red granules can be found in the epithelium (can you find them?). These are not eosinophils. They are specialized endocrine cells that secrete hormones and growth factors important to the GI tract (called "enteroendocrine cells".)