LE cell test and DEMONSTRATION , Introduction, Principle, Procedure, Results

DEMONSTRATION OF LE CELLS:

• Introduction

  Principle

  Specimen

  Procedure

  Results 

Introduction:-

An LE cell is a neutrophil which contains a basophilie, opaque, homogeneous mass in its cytoplasm. The nucleus is pushed towards the periphery and appears crescent shaped around the ingested mass. An LE cell is formed when the LE factor combines with nuclear protein in the presence of phagocytic leucocytes. The LE factor is the IgG antibody to nucleoprotein derived either from granulocytes or lymphocytes. LE cells can be found in about 60 to 75 % of patients with systemic lupus erythematosus (SLE). They are also produced in response to various drugs such as procainamide and hydralazine.

The test consists of incubation of patient's plasma containing LE factor with patient's leucocytes. The smears are prepared for the presence of LE cells. 

Specimen:  

Collect about 10 ml of blood in heparinised tube containing 10 glass beads. The LE factor does not act on leucocytes unless they are slightly damaged. This is achieved by rotating the whole blood with glass beads. 

Technique

(i) Rotate the blood sample with the beads in the tube for 30 minutes either manually or on a rotator. 

(ii) Incubate at 37°C for 30 minutes to 1 hour, shaking intermittently.

(iii) Transfer the blood to a Wintrobe tube using a pasteur pipette and centrifuge at 1,500 rpm for 15 to 20 minutes.

(iv) Discard the layer of plasma at the top.Carefully withdraw the cells from the buffy coat and prepare thin smears.

(v) Examine under oil immersion objective for LE cells which are indicated by bluish purple mass in the cytoplasm of a neutrophil.

Note

The LE cell test is neither completely specific, nor very sensitive for the diagnosis of SLE. More specific and sensitive tests, such as immunofluorescence and latex agglutination for the detection of antinuclear antibody (LE factor) are available.

Latex Agglutination Test for the Detection of LE Factor:The test employs agglutination of latex particles coated with deoxyribonucleoprotein (DNP) by LE factor, which is an antibody to DNP.