Differential recovery of antibody production potential after sublethal, whole-body irradiation of mice

Area of Science:

• Immunology
• Radiation Biology
• Cellular Immunology

Background:

• Sublethal whole-body irradiation significantly impacts immune function.
• Understanding the kinetics of immune recovery post-irradiation is crucial for predicting health outcomes.
• Specific B-cell responses, particularly to T-cell-independent antigens, are sensitive indicators of immune status.

Purpose of the Study:

• To investigate the recovery of immune responses in mice after sublethal whole-body irradiation.
• To characterize the specific types of immune responses affected by irradiation, focusing on T-cell-dependent and T-cell-independent antigens.
• To elucidate the cellular mechanisms underlying the impaired immune recovery, particularly for T-cell-independent type-2 antigens.

Main Methods:

• Mice were subjected to whole-body irradiation (550 rad) and subsequently immunized with sheep erythrocytes (SE) or polyvinylpyrrolidone (PVP) at various time points.
• Direct plaque-forming cell (PFC) responses were quantified to assess antigen-specific immune activity.
• Adoptive transfer experiments using bone marrow, fetal liver, or spleen cells were performed to evaluate cellular reconstitution.
• Responses to additional antigens, including T-cell-dependent, T-cell-independent type-1, and T-cell-independent type-2 antigens, were analyzed.

Main Results:

• Irradiated mice showed no immune response at 15 days post-irradiation (PI).
• By 30 days PI, responses to the T-cell-dependent antigen SE recovered to 40-126% of normal, while responses to the T-cell-independent type-2 antigen PVP remained impaired (3-38% of normal).
• Impaired PVP response was observed even after doses as low as 200 rad and in both athymic and euthymic mice.
• Adoptive transfer of normal bone marrow, fetal liver, or spleen cells, particularly Ig+ enriched cells, repaired the impaired PVP response.
• Mice showed impaired responses to T-cell-independent type-2 antigens (PVP, pneumococcal polysaccharide, bacterial lipopolysaccharide) but recovered responses to T-cell-dependent and T-cell-independent type-1 antigens by 30 days PI.

Conclusions:

• Whole-body irradiation induces a specific defect in T-cell-independent type-2 B-cell responses that persists for at least 30 days.
• This defect is distinct from general immune suppression and resembles the immunodeficiency seen in CBA/N mice with X-linked immunodeficiency.
• The recovery of these specific B-cell responses is dependent on the reconstitution of appropriate immune cell populations, highlighting the radiosensitivity of certain B-cell subsets.