Trypanosoma congolense infection in sheep: cellular phenotypes in lymph and lymph nodes associated with skin reactions

Area of Science:

• Veterinary Immunology
• Parasitology
• Immunology

Background:

• Trypanosoma congolense is a significant veterinary pathogen causing significant economic losses in livestock.
• Understanding the host immune response to trypanosome infections is crucial for developing effective control strategies.

Purpose of the Study:

• To investigate the dynamic changes in lymphocyte populations within the lymphatic system during experimental Trypanosoma congolense infection in sheep.
• To characterize the cellular immune response in afferent and efferent lymph draining the site of infection.

Main Methods:

• Intradermal inoculation of sheep with metacyclic Trypanosoma congolense.
• Cannulation of afferent and efferent lymphatic ducts to collect lymph.
• Immunofluorescent staining and flow cytometry to analyze lymphocyte phenotypes (CD4+, CD8+, surface immunoglobulin).

Main Results:

• Localized skin reactions (chancres) and lymphadenopathy developed 7 days post-infection.
• Trypanosomes were detected in lymph from day 3-5 and persisted.
• Increased cellular output in both afferent and efferent lymph.
• Afferent lymph showed an early increase in T cells (CD4+, CD8+), followed by lymphoblasts and immunoglobulin-bearing cells during chancre regression.
• Efferent lymph showed a predominant increase in surface immunoglobulin-bearing cells.

Conclusions:

• The study elucidates the sequential lymphocyte dynamics in response to Trypanosoma congolense infection in sheep.
• Both T cell and B cell responses are involved in the immune response within the draining lymphatics.
• These findings contribute to understanding the pathogenesis of trypanosomiasis and potential immune evasion strategies of the parasite.