Granulocytes have two types of granules primary and secondary. Primary granules are azurophilic, most numerous and prominent at the promyelocyte stage (see morphology of myeloid precursors) and diminish in number with further maturation. As the granulocyte matures the staining characters of the primary granules changes. They initially become violet and then became inapparent because they fail to take up stain. The secondary granules appear in the myelocytes and persist for the rest of the ice of the granulocyte. Neutrophils have fine pink secondary granules.
In conditions of intense stimulation of neutrophil maturation the primay granules may continue to take up stain in mature neutrophil because of a higher concentration of acid mucosubstances. These are called as toxic granules and the change called toxic change. The toxic granules are so called because they were first described in patients with gram negative sepsis and endotoxemia but may be found under conditions of intense stimulation of neutrophil production. The may be seen in
- Infection
- Inflammatory diseases
- Pregnancy
- Use of haemopoietic growth factors (G-CSF or GM-CSF)
