Flow cytometric analysis of an immunodeficiency disorder affecting juvenile llamas.

The present study was undertaken to characterize the immune system of llamas and alpacas and establish the basis for an immunodeficiency disorder affecting juvenile llamas. Flow cytometric (FC) analysis of the immune system with a panel of monoclonal antibodies (mAbs) revealed the immune system of llamas and alpacas is similar in leukocyte subset composition to that in ruminants. Peripheral blood mononuclear cells in adults are comprised of surface immunoglobulin (sIg(+)) B-cells (31%+/-8 S.D.), alphabeta T-cells (27%+/-12 S.D.), WC1(+) gammadelta T-cells (16%+/-11 S.D.), and 5-16% monocytes. In contrast to cattle, goats, and sheep, however, the frequency of WC1(+) gammadelta T-cells is not high in juveniles but similar to the frequency in adults. Also, sIg(+) B-cells are present in high concentration in juveniles (43%+/-11 S.D. ). Expression of major histocompatibility class II molecules on resting T-cells was low or absent. Comparative analysis of peripheral blood lymphocyte composition in normal juvenile llamas and llamas presenting with the signs of the juvenile llama immunodeficiency syndrome (JLIDS) revealed the concentration of B-cells is extremely low (1-5%) in affected animals. The findings suggest JLIDS is attributable to an autosomal recessive genetic defect in the development of B-cells.

Kinetic characteristics of beta-carotene uptake after an injection of beta-carotene in pigs.

Two experiments were conducted to study the uptake of beta-carotene in plasma, lipoproteins, and blood cells in pigs (50 to 55 kg; n = 40) after an i.m. injection of 0, 10, 20, or 40 mg of beta-carotene. Blood was sampled at 0, 3, 6, 12, 24, and 48 h postinjection. beta-Carotene was not detectable in plasma, lipoproteins, or blood cells of control pigs. However, concentrations of beta-carotene in plasma and lipoproteins increased in a dose-related manner in injected animals. Distribution of beta-carotene in the lipoproteins changed with time postinjection. The beta-carotene associated with very low density lipoproteins increased and that in low density lipoproteins decreased with time in treated pigs. Concentrations of beta-carotene in lymphocytes of treated pigs also increased within 3 h postinjection. The profile of beta-carotene in lymphocytes was different from that observed in plasma and lipoproteins. Carotene was not detectable in neutrophils and erythrocytes. Treatment did not alter concentrations of retinol or alpha-tocopherol in plasma, lipoproteins, or blood cells. Therefore, lymphocytes specifically take up beta-carotene, thereby suggesting a possible role of beta-carotene in this immune cell.

Subcellular distribution of beta-carotene, retinol, and alpha-tocopherol in porcine lymphocytes after a single injection of beta-carotene.

The subcellular distribution of beta-carotene, retinol, and alpha-tocopherol in lymphocytes was studied in pigs (50 to 55 kg) injected once with 0, 20, or 40 mg of beta-carotene. Blood was sampled at 0, 24, 48, and 72 h postinjection. Plasma beta-carotene in treated pigs peaked at 24 h and decreased rapidly thereafter. Beta-carotene was found in all subcellular fractions of lymphocytes. Concentrations in nuclei mirrored changes in plasma. However, beta-carotene in mitochondria and cytosol peaked at 24 h, whereas that in microsomes peaked at 48 h. Concentrations in the latter three subcellular fractions remained high at 48 and 72 h even though plasma beta-carotene had decreased to very low concentrations. Peak concentrations of beta-carotene were highest in the nuclei, intermediate in the mitochondria and microsomes, and lowest in the cytosol. Treatment did not influence concentrations of retinol or alpha-tocopherol in the various subcellular fractions. These data provide more compelling evidence for the possible role of beta-carotene in lymphocytes.

Modulatory effects of dietary beta-carotene on blood and mammary leukocyte function in periparturient dairy cows.

Beginning 4 wk prior to predicted calving, 14 Holstein cows per treatment were fed diets 1) unsupplemented (control) or supplemented daily with 2) 300 mg of beta-carotene, 3) 600 mg of beta-carotene, or 4) 120,000 IU of vitamin A. Blood was collected around calving on wk -4, -2, -1, 0 (within 24 h postcalving), 1, 2, and 4 for isolation of lymphocytes and neutrophils and for the analysis of plasma vitamins. Lacteal secretions were collected on wk 0, 1, 2, and 4 for the isolation of phagocytes. Cows supplemented with 600 mg of beta-carotene had higher concentrations of plasma beta-carotene and retinol than did unsupplemented cows. Supplemental vitamin A increased plasma retinol on wk 4 and decreased plasma beta-carotene on wk -1 and 0. Treatment did not affect concentrations of plasma alpha-tocopherol. Blood lymphocyte proliferation in response to concanavalin A, phytohemagglutinin, and pokeweed mitogen during the peripartum period was higher in cows supplemented with beta-carotene than in unsupplemented controls. Phagocytic activity of blood neutrophils was enhanced on wk 1 in cows fed 300 mg of beta-carotene. Intracellular killing by blood neutrophils was enhanced in cows supplemented with beta-carotene (wk 0) and vitamin A (wk 0 and 1). Iodine uptake and nitroblue tetrazolium reduction by blood neutrophils was stimulated in cows supplemented with beta-carotene. Phagocytic activity, iodine uptake, and nitroblue tetrazolium reduction by mammary phagocytes from all cows generally were lower postpartum than on the day of calving. The incidence of retained placenta and metritis was higher for unsupplemented cows than for cows supplemented with beta-carotene. Therefore, dietary beta-carotene can elevate peripartum concentrations of blood beta-carotene, enhance host defense mechanisms by potentiating lymphocyte and phagocyte function, and decrease the incidence of certain reproductive disorders.