Mast cells, basophils and eosinophils

Wednesday - November 24, 2010

Mast cells, basophils and eosinophils in innate immunity

Basophils, mast cells and eosinophils are white blood cells involved in the innate immune response especially associated with allergy and asthma. These cells are characterized by the presence of lobulated nuclei and secretory granules in the cytoplasm. Upon stimulation these granules release their contents (degranulation), predominantly mediators and cytokines. They are key effector cells in IgE-associated immune response and participate in the innate immune responses to many pathogens, including bacteria and viruses.

Basophils
Although basophils constitute less than 1 % of circulating blood leukocytes, they gain more recognition as key players in the immune system. Basophils are often recruited to the site of allergic inflammation. Furthermore, basophils are candidate effector cells for the immune response against parasites and are a major source of the typical Th2 cytokine IL-4 during parasite infections.

Figure 1
Basophils are recruited into the draining lymph nodes by unknown mechanisms and are stimulated directly or indirectly, before or after lymph node entry, by allergens with enzymatic activity. This process results in the secretion by basophils of factors that favor TH2 differentiation. Allergens may also induce the selective maturation of antigen-bearing DCs that might further assist in TH2 differentiation. TN, naive T cells. Nat Immunol 2008, 9: 223

The unavailability of mouse basophil-specific antibodies has long hampered the progress in clarifying the critical roles of basophils. Monoclonal antibodies Ba91 and Ba103 recognize the CD200 receptor type 3 (CD200R3). CD200R3 functions as an activating receptor on mast cells and basophils to regulate IgE-independent immune responses in cooperation with an inhibitory receptor CD200R. mAbs Ba91 and Ba103 selectively stain basophils from the peripheral blood, spleen, and bone marrow and mast cells form the peritoneal cavity and skin, but not from the intestine. In vitro incubation of Ba91 or Ba103 together with basophils or mast cells results in degranulation of the cells. Interestingly, intravenous injection of Ba103 into mice results in depletion of basophils but not mast cells.

In conclusion, mAbs Ba91 and Ba103 are usefool tools to study basophil function in a variety of mice species.

Mast cells
Like basophils and eosinophils, mast cells originate from hematopoietic stem cells in the bone marrow. However, they complete their differentiation in the peripheral tissues. Mast cells have been implicated in rheumatoid arthritis, multiple sclerosis, atherosclerosis, inflammatory bowel disease and angiogenesis.

Eosinophils
Eosinophils are granulocytes that develop during hematopoiesis in the bone marrow before migrating into blood. They constitute ~1-3 % of the total white blood cells and are characterized by specific cytoplasmic granules that contain a series of cationic toxins able to kill many targets, including helminths, protozoa, bacteria and other cells. In bronchial asthma, predominantly major basic protein (MBP) is released resulting in tissue abnormalities. The number of these cells (eosinophil count) increases in certain illnesses, including allergies, asthma, Addison's disease, sarcoidosis, parasite infections, drug reactions, and connective tissue diseases (such as rheumatoid arthritis and scleroderma).

Cat. No.	Product	Applications
HM1103	Monoclonal antibody against Mouse CD200R3, clone Ba103	W IP FC FS
HM1104	Monoclonal antibody against Mouse CD200R3, clone Ba91	W IP FC FS

W = Western Blotting; IP = ImmunoPrecipitation; FC = Flow Cytometry; FS = Functional Studies (agonistic)