Partial characterization of ovine intrauterine suppressor cells

Area of Science:

• Reproductive immunology
• Cell biology
• Immunology

Background:

• Uterine cells play a role in immune regulation during pregnancy.
• Understanding uterine immune cell function is crucial for reproductive success.

Purpose of the Study:

• To investigate the immunomodulatory properties of ovine uterine cells.
• To identify the cell types responsible for suppressing lymphocyte proliferation.
• To determine the nature of the suppressor factor released by uterine cells.

Main Methods:

• Fractionation of ovine uterine cells using Percoll density gradients.
• Co-culture of uterine cells with phytohemagglutinin (PHA)-stimulated peripheral blood lymphocytes (PBLs).
• Flow cytometry to identify lymphocyte markers (CD5+, CD4+, CD8+).
• Assay for transforming growth factor beta (TGFbeta) activity in cell supernatants.

Main Results:

• Low-density uterine cells (1.002-1.056 g/ml) suppressed PHA-induced PBL proliferation.
• The majority of these suppressor cells were small (<= 5.2 microm).
• Suppressor cell populations had lower percentages of conventional T-lymphocyte markers.
• Uterine cell supernatants contained suppressor factors, but these lacked TGFbeta activity and were not affected by antibody treatments.

Conclusions:

• Low-density uterine cells from cyclic and pregnant ewes possess significant suppressor activity on PBL proliferation.
• The identified suppressor cells are unlikely to be conventional T-, B-, or NK-like lymphocytes.
• Uterine cells release non-TGFbeta suppressor factors, indicating a unique immunoregulatory mechanism in the ovine uterus.