Cellular pathology of allergic airway inflammatory responses to ovalbumin (OVA) following adoptive transfer of CD4 + T lymphocytes to naive rats

Abstract

Rationale CD4 + T lymphocytes play an important role in the orchestration of allergic, airway inflammation. This study characterizes the cellular pathology of the inflammatory response following adoptive transfer of OVA-activated CD4 + T lymphocytes to naïve rats. Methods Mediastinal lymph nodes (LN) were taken from OVA sensitized and challenged Brown Norway (BN) rats. After 48h in culture with OVA, populations of enriched CD4 + T lymphocytes (81% CD4 +), mixed LN cells (44% CD4 +), CD4 − LN cells (0.4% CD4 +) or saline were injected into naïve rats. Rats were challenged with aerosolized OVA on 3 consecutive days. Cells within BALF were quantified and lung tissue histopathology assessed. Results Administration of CD4 − LN cells or saline produced a mild inflammatory response in the lung tissue following OVA challenge. Adoptive transfer of enriched CD4 + or mixed LN cells produced a significant increase in BALF eosinophils (p<0.05) and a marked leukocyte infiltration into the lung tissue to OVA. The CD4 + or mixed LN group was associated with peri-vascular and bronchiolar inflammation, BALT expansion and sub-mucosal leucocyte infiltration. These responses were more marked in the CD4 + group. The presence of significant bronchiolar metaplasia in the CD4 + group suggests that a more mature response was elicited. Conclusion Histopathology assessment of the lung tissue clearly demonstrated a role for CD4 + T lymphocytes in the rate of maturation and severity of the inflammatory response within the lung tissue. Inclusion of the above endpoints in adoptive transfer studies provides a model to investigate the role of CD4 + T cells in the pathogenesis of allergic, airway inflammation.