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Flow microfluorometry analysis of alterations in T-lymphocyte subsets during murine listeriosis
Abstract:
C57BL/6 mice were infected intravenously with 6 X 10(3) Listeria monocytogenes organisms. As early as day 3 of infection, there was a marked reduction in the number of lymphocytes recovered from the peripheral blood, bone marrow, and thymuses of infected animals. Concomitantly, there was an increase in the number of splenic lymphocytes. By day 14, both the total and differential cell counts were similar in both infected and normal animals. Flow microfluorometric studies comparing the Thy-1.2, Lyt-1, Lyt-2, and surface immunoglobulin (SIg) phenotypes of lymphocytes from normal and infected mice were performed. Between days 3 and 5, there was a decrease in the percentage of Thy-1.2+ cells in the spleens of L. monocytogenes-infected animals. Conversely, the percentages of Lyt-1+, Lyt-2+, and SIg+ cells remained constant. At day 7 of infection, the percentage of Thy-1.2+ splenocytes was within normal limits, and at day 10, the percentage of Thy-1.2+ cells was elevated slightly. The absolute numbers of Thy-1.2+ cells were comparable in both infected and normal animals at early stages (days 3 to 5) of L. monocytogenes infection, but there was a marked elevation of Thy-1.2+ splenocytes at days 7 to 14 of infection. Lyt-1+, Lyt-2+, and SIg+ splenocytes increased in absolute numbers as early as day 3 of infection and were still elevated at day 14. Adrenalectomy before infection had no effect on the results obtained, suggesting that these changes were not mediated by endogenous steroids.
Insights
Listeria monocytogenes infection causes early lymphocyte reduction in blood, bone marrow, and thymus, with splenic lymphocyte changes. These immune cell dynamics, including Thy-1.2+, Lyt-1+, Lyt-2+, and SIg+ phenotypes, normalize by day 14.
Area of Science:
- Immunology
- Microbiology
- Cell Biology
Background:
- Listeria monocytogenes is a bacterial pathogen that can cause systemic infection.
- Understanding the host immune response to infection is crucial for developing effective treatments.
- Lymphocyte populations undergo dynamic changes during bacterial infections.
Purpose of the Study:
- To investigate the changes in lymphocyte populations and phenotypes in mice infected with Listeria monocytogenes.
- To determine the temporal dynamics of immune cell alterations during the course of infection.
- To assess the role of endogenous steroids in mediating these immune changes.
Main Methods:
- Intravenous infection of C57BL/6 mice with Listeria monocytogenes.
- Analysis of lymphocyte counts in peripheral blood, bone marrow, thymus, and spleen.
- Flow microfluorometric analysis of lymphocyte surface markers: Thy-1.2, Lyt-1, Lyt-2, and surface immunoglobulin (SIg).
- Adrenalectomy was performed prior to infection in a subset of animals.
Main Results:
- A significant reduction in lymphocytes was observed in blood, bone marrow, and thymus by day 3 post-infection.
- Splenic lymphocyte numbers increased early in infection.
- Flow cytometry revealed a transient decrease in the percentage of Thy-1.2+ cells in the spleen (days 3-5), with subsequent elevation (days 7-14).
- Percentages of Lyt-1+, Lyt-2+, and SIg+ cells remained constant, but their absolute numbers increased early and remained elevated.
- Adrenalectomy did not alter the observed immune cell changes.
Conclusions:
- Listeria monocytogenes infection induces significant, time-dependent alterations in lymphocyte distribution and phenotype.
- The observed changes in splenic lymphocyte populations, particularly the increase in absolute numbers of Lyt-1+, Lyt-2+, and SIg+ cells, suggest a complex immune response.
- Endogenous steroids do not appear to mediate these infection-induced immune cell dynamics.