<P> They primarily deal with parasitic infections . Eosinophils are also the predominant inflammatory cells in allergic reactions . The most important causes of eosinophilia include allergies such as asthma, hay fever, and hives; and also parasitic infections . They secrete chemicals that destroy these large parasites, such as hook worms and tapeworms, that are too big for any one WBC to phagocytize . In general, their nucleus is bi-lobed . The lobes are connected by a thin strand . The cytoplasm is full of granules that assume a characteristic pink - orange color with eosin staining . </P> <P> Basophils are chiefly responsible for allergic and antigen response by releasing the chemical histamine causing the dilation of blood vessels . Because they are the rarest of the white blood cells (less than 0.5% of the total count) and share physicochemical properties with other blood cells, they are difficult to study . They can be recognized by several coarse, dark violet granules, giving them a blue hue . The nucleus is bi - or tri-lobed, but it is hard to see because of the number of coarse granules that hide it . </P> <P> They excrete two chemicals that aid in the body's defenses: histamine and heparin . Histamine is responsible for widening blood vessels and increasing the flow of blood to injured tissue . It also makes blood vessels more permeable so neutrophils and clotting proteins can get into connective tissue more easily . Heparin is an anticoagulant that inhibits blood clotting and promotes the movement of white blood cells into an area . Basophils can also release chemical signals that attract eosinophils and neutrophils to an infection site . </P> <P> Lymphocytes are much more common in the lymphatic system than in blood . Lymphocytes are distinguished by having a deeply staining nucleus that may be eccentric in location, and a relatively small amount of cytoplasm . Lymphocytes include: </P>

What do white blood cells release to attract other white blood cells