Flow cytometric analysis of an immunodeficiency disorder affecting juvenile llamas

The present study was undertaken to characterize the immune system of llama s and alpacas and establish the basis for an immunodeficiency disorder affe cting juvenile llamas. Flow cytometric (FC) analysis of the immune system w ith a panel of monoclonal antibodies (mAbs) revealed the immune system of l lamas and alpacas is similar in leukocyte subset composition to that in rum inants. Peripheral blood mononuclear cells in adults are comprised of surfa ce immunoglobulin (sIg(+)) B-cells (31%+/-8 S.D.), alpha beta T-cells (27%/-12 S.D.), WC1(+) gamma delta T-cells (16%+/-11 S.D.), and 5-16% monocytes . In contrast to cattle, goats, and sheep, however, the frequency of WC1(+) gamma delta T-cells is not high in juveniles but similar to the frequency in adults. Also, sIg(+) B-cells are present in high concentration in juveni les (43%+/-11 S.D.). Expression of major histocompatibility class II molecu les on resting T-cells was low or absent. Comparative analysis of periphera l blood lymphocyte composition in normal juvenile llamas and llamas present ing with the signs of the juvenile llama immunodeficiency syndrome (JLIDS) revealed the concentration of B-cells is extremely low (1-5%) in affected a nimals. The findings suggest JLIDS is attributable to an autosomal recessiv e genetic defect in the development of B-cells. (C) 2000 Elsevier Science B .V. All rights reserved.