Memory responses to ovalbumin-immunization in Mojave desert tortoises

Area of Science:

• Immunology
• Herpetology
• Comparative immunology

Background:

• Mojave desert tortoises possess high levels of B1 lymphocytes and natural antibodies (NAbs).
• Understanding B2 lymphocyte activity is crucial for assessing adaptive immune memory in reptiles.
• Ovalbumin (OVA) with Freund's adjuvant was used to mimic bacterial antigen responses.

Purpose of the Study:

• To quantify B2 lymphocyte activity during primary and secondary immunizations in desert tortoises.
• To investigate the development of immunological memory, specifically long-term antibody increases and B2 memory cell features.
• To assess the role of B1 lymphocytes in the humoral immune response of Gopherus agassizii.

Main Methods:

• Three groups of tortoises were immunized with OVA: twice, once, or sham-immunized.
• Antibody production, B cell numbers, and proliferation in response to OVA were measured.
• Analysis focused on OVA-specific antibody titers, avidity, and circulating OVA-specific B cells.

Main Results:

• Secondary responses were faster but did not increase antibody titer or avidity.
• Both immunized groups showed a long-term elevation in antibodies.
• No significant effect of immunization or number of immunizations on OVA-stimulated B cell numbers was observed; however, antibody secretion by B lymphocytes was affected by immunization.

Conclusions:

• Desert tortoises exhibit a robust constitutive B1 lymphocyte response, capable of being stimulated by immunization.
• Evidence for B2 memory lymphocytes was not found, as cells did not proliferate upon stimulation.
• Natural antibodies (NAbs) increased due to B1 lymphocyte priming with adjuvant, confirming their role in the initial immune response.