Comparison of the direct antiglobulin rosetting reaction (DARR) and direct immunofluorescence (DIF) for demonstration of sIg-bearing lymphocytes in pigs, sheep and cattle.

Tests with untreated and trypsin-treated red cells (rbc) from a variety of species showed that anti-Ig-coupled pig RBC are good indicator cells for the study of ruminant blood sIg + lymphocytes by the DARR test; coupled donkey and rabbit RBC are suitable for investigating pig lymphocytes. The different species showed the following percentages of sIg + lymphocytes (M +/- SE) by direct immunofluorescence (DIF) and the direct antiglobulin rosetting reaction (DARR) respectively:pigs 9.2 +/- 0.7% and 16.3 +/- 1.2%; sheep 20.2 +/- 1.2% and 33.1 +/- 1.6%; Cattle 13.5 +/- 1.4% and 28.9 +/- 3.5%. The mean ratio of sIg + lymphocytes shown by the two tests (DARR/DIF) for each species was 1.80 +/- 0.08 for pigs, 1.73 +/- 0.7 for sheep and 2.15 +/- 0.18 for cattle. Preincubation of pig and sheep lymphocytes at 37 degrees for 1 h did not alter the proportion of sIg + lymphocytes detected by either test. Thus the DARR test reveals a further population of sIg + lymphocytes in addition to that detected by immunofluorescence, whose number is proportional to the B population as measured by DIF and whose sIg is intimately associated with the membrane.