Basophils

Basophils vary in diameter from 12 μm to 15 μm but are usually slightly smaller than neutrophils. Their nuclei are less heterochromatic than other granulocytes and usually consist of 3 irregular lobes which are often obscured by the large, dark-staining cytoplasmic granules. The specific granules of basophils are their most characteristic feature.

These granules have irregular shapes and vary in size; the largest are the size of the specific granules of eosinophils, the smallest nearly as small as those of neutrophils. The granules stain metachromatically and appear reddish-violet to nearly black in stained blood smears.

The specific granules of basophils (like those of the mast cells of connective tissue) contain heparin and histamine, which may be released by exocytosis in response to certain types of antigenic stimuli. The granules may contain inclusions, but they appear more homogeneously electron-dense than do those of eosinophils.

Monocytes

Monocytes are often confused with large lymphocytes, but they are larger and constitute only 3-8 % of the white blood cells in healthy adults. Monocytes are found only in the blood, but they remain in circulation for less than a week before migrating through capillary walls to enter other tissues or to become incorporated in the lining of sinuses. Once outside the bloodstream, they become phagocytic and apparently do not recirculate. Monocytes are the direct precursors to macrophages. 

The mononuclear phagocyte system (portions of which were formerly referred to as the reticuloendothelial system) consists of monocyte-derived phagocytic cells distributed throughout the body. Examples include the Kupffer cells of the liver and some of the macrophages of connective tissues.

Bilirubin

Bilirubin, a product of hemoglobin metabolism, is conjugated in the liver to the mono- and diglucuronides and excreted in bile. Some conjugated bilirubin is bound to serum albumin, so-called D (delta) bilirubin. Elevated serum bilirubin occurs in liver disease, biliary obstruction, or hemolysis. 

Normal Range: 0.1-1.2 Direct (conjugated to glucuronide) bilirubin, 0.1-0.4 mg/dL (< 7 µmol/L); Indirect (unconjugated) bilirubin, 0.2-0.7 mg/dL (< 12 µmol/L) mg/dL

increased in: Acute or chronic hepatitis, cirrhosis, biliary tract obstruction, toxic hepatitis, congenital liver enzyme abnormalities (Dubin-Johnson, Rotor's, Gilbert's, Crigler-Najjar syndromes), fasting, hemolytic disorders. Hepatotoxic drugs. 

 

Additional: Assay of total bilirubin includes conjugated (direct) and unconjugated (indirect) bilirubin plus delta bilirubin (conjugated bilirubin bound to albumin). It is usually clinically unnecessary to fractionate total bilirubin. The fractionation is unreliable by the diazo reaction and may underestimate unconjugated bilirubin. Only conjugated bilirubin appears in the urine and it is indicative of liver disease; hemolysis is associated with increased unconjugated bilirubin. Persistence of delta bilirubin in serum in resolving liver disease means that total bilirubin does not effectively indicate time course of resolution