Lymphocytes from ponies experimentally infected with equine herpesvirus 1: subpopulation dynamics and their response to mitogens.

The research puts six pony foals, that have no existing immunity against equine herpesvirus type 1, under study to observe the changes in their lymphocyte populations post inoculation with the virus. The study discovers the occurrence of transient leukopenia and identifies differences in the behavior of T and B lymphocyte subpopulations during different stages of the disease.

Methodology

• The study involves six pony foals free from any detectable serum neutralization antibody against equine herpesvirus type 1. This prerequisite ensures that the ponies’ immune system has not been exposed to this virus before.
• The ponies are inoculated with the virus, and their immune response is closely monitored.

Observations Post Inoculation

• After infection, the ponies displayed typical signs of respiratory tract disease, indicating the successful transmission of the virus.
• A transient leukopenia, a temporary decrease in the count of white blood cells, was observed, affecting lymphocytes and neutrophils.
• The lowest leukocyte count was reached between the third and fifth day post-inoculation, but it returned to normal between the eighth and tenth day.

Dynamics of Lymphocyte Subpopulations

• Detailed examination of white blood cells revealed that both T and B lymphocytes decreased during leukopenic onset but recovered as the leukopenic phase ended.
• Interestingly, during the period of leukopenia, the ratio of T to B lymphocytes remained stable, with T lymphocytes accounting for 70% to 80% and B lymphocytes accounting for 20% to 30% of the total count.

Response to Mitogens

• The lymphocyte blastogenic response to mitogens, substances that encourage cell division, peaked between the second and fifth day, then decreased to baseline or below by the seventh day.
• Responses from T lymphocytes and mixed lymphocyte preparations were nearly identical. However, two ponies showed an increase in B lymphocytes up to 40%-50% during the recovery phase, as well as an unusually high mixed lymphocyte response to mitogens and a lower T lymphocyte response.

The research concludes by discussing the significance of the varying responses noted in the two subpopulations of lymphocytes during the different stages of the disease.