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The purpose of this study was to investigate the influencing factors for lymphocyte subset distribution in growing and lactating cows.
Methods: 15 genetically identical Holstein Friesian twin cows were either obtained by embryo splitting or purchasing. At the age of three months the twins were each divided into two groups. Group one was restrictively fed with silage and hay, group two got intensive nutrition with concentrates, silage and hay. Blood samples from the animals were collected every four weeks by puncture of the jugular vein. Mononuclear cells were isolated from the peripheral blood using the Ficoll density gradient centrifugation. The following commercial monoclonal antibodies were used: FITC-labeled mouse anti-bovine CD4 (Serotec, Clone CC4), FITC-labeled mouse anti-bovine CD8 (Serotec, Clone CC63) and unlabeled mouse anti-bovine CD21 (Serotec, Clone CC21). For determination of CD21 a second rabbit anti-mouse IgG-antibody labeled with RPE was used (Serotec). Flow cytometry was performed using FACS Calibur (Becton Dickinson).
Results: The lymphocyte subset patterns showed plain variations until the age of five months. Later on they stayed nearly constant. Likewise no environmental influence on lymphocyte subset distribution could be noticed after an age of nine months, even if retarded development in restrictively fed calves took place. Calving and lactation had no influence on CD4+ and CD21+ lymphocytes, only CD8+ cells showed a slight decrease in the beginning of the lactation period. The similar development within different twin pairs demonstrated a strong genetic influence on lymphocyte subset distribution. Between the different pairs we found great variations.
Conclusion: An influence of age on lymphocyte subset distribution was observed only in the growth when the immune system is still developing. After an age of five months no significant differences could be found. In the same way no significant effects of intensive or restrictive feeding on lymphocyte subsets could be demonstrated. In the course of time we found a strong correlation between the feeding groups. This might be explained with too little differences between the feeding intensities. The similar development of the twin pairs’ lymphocyte subsets and the significant differences between the pairs can be used as proof of the significant genetic influence on T-helper cell, cytotoxic T-cell and B-lymphocyte relations. If these features are heritable they could be utilized for selection of immune adjusted animals.