In case you didn't know, leukocytes are the white blood cells that form an important part of our immune system and their primary function is to tackle infection and disease-causing foreign particles and pathogenic organisms that invade our body. There are various different types of leukocytes inside our bodies and each type of leukocytes have a different immune function assigned to it. To be specific, based upon their structure and functions, there are seven different types of leukocytes, each performing its own individual assignment to keep the body safe from infections, allergens and pathogens. These are Neutrophils (which fight off bacterial and fungal pathogens), Eosinophils (which are responsible for regulating allergic responses and are entrusted with fighting larger parasitic organisms within the body), Basophil (which trigger inflammatory allergic responses by releasing histamines in the blood stream), Lymphocytes (which take charge of the overall cellular immune responses by releasing B, T and Th cells and regulating their functions), Monocytes (activate T cells in the form of dendritic cells and engulf and absorb pathogenic remnants from cells in the form of monophages), Monophages and Dendritic Cells (both of which occur as a result of Monocyte differentiation).
However, based upon the most prominent aspect of distinction based upon cellular biology, there are two types of white blood cells - granular and agranular. Granular leukocytes or Granulocytes (as they are commonly referred to) are those leukocytes in which staining granules are present in the cytoplasm of the cells. Agranular leukocytes (or Agranulocytes), on the other hand, are those white blood cells that lack staining granules. Now, before we proceed towards discussing what an agranular white blood cell is, let me tell you what these staining granules are and what their function is. These granules are chemical enzymes that are packed within membranes and their sole function is to absorb the particles of various essential molecules and nutrients that are engulfed by cells.
What is an Agranular White Blood Cell?
As mentioned above, an agranulocyte is a white blood cell in which the specific membrane-wrapped packets of enzymes that absorb molecular particles engulfed by cells are absent. There are two distinct types of agranular leukocytes in our body - Lymphocytes and Monocytes. The Monocytes further differentiate to form Macrophages and Dendritic Cells.
Lymphocytes form a significant part of the lymphatic system and their chief function is to release antibodies that fight infections and neutralize pathogenic organisms, initiation of cell mediated immune response that does not involve the release of antigens and works by activating Natural Killer Cells and Macrophaphages. Some lymphocyte variant of agranular leukocyte examples would include B Cells (that actually release antigens), T Cells (that perform the cell mediated immunity functions that exclude the release of antigens) and Natural Killer Cells (that are responsible for detecting and rejecting tumor cells and cells that are contaminated by viral pathogens).
Monocytes are agranulocytes that literally eat up and absorb pathogenic remains and unwanted cell debris and also alert the immune system to the presence of pathogens by presenting small samples of foreign antigen particles to the T lymphocytes. There are two types of monocytes - Macrophages and Dendritic Cells. Macrophages are the ones that eat up and digest the pathogenic remnants and other unwanted cellular particles while Dendritic Cells perform the T lymphocyte activating functions.
The remaining types of leukocytes - Neutrophils, Eosinophils and Basophils - are granular and they directly attack the common bacterial, fungal, parasitic and allergic pathogens. The granular white blood cells functions and modus operandi differ considerably from those of agranulocytes, although the end purpose of both types of white blood cells is the same - fighting diseases and infections. All types of white blood cells, be it granular or agranular, are produced by the bone marrow.