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In vitro studies on the adjuvanticity of Brucella fractions
Abstract:
Two Brucella fractions, the murein-linked fraction PI and the murein-free fraction SF, behave as in vitro adjuvants for primary anti-sheep erythrocyte responses: added to Mishell and Dutton-type cultures of spleen cells from B6/DB F1 mice they significantly enhance the number of direct anti-sheep erythrocyte PFC observed on day 5. They exert both nonspecific, polyclonal activating effects and antigen-dependent specific adjuvanticity. These two functions, however, differ in their dose responses and in their cellular requirements and can therefore be dissociated. Thus, polyclonal activation requires high doses of the "adjuvant fraction," is enhanced by adherent-cell depletion, and is not impaired by T-cell depletion. Specific adjuvanticity, on the other hand, requires lower doses of the adjuvant fractions (very high doses are in fact suppressive) and is T-cell and adherent-cell dependent. Moreover, adjuvanticity can be transferred to unstimulated spleen cells (or restored in adherent-cell-depleted populations) by PI- or SF-stimulated adherent cells or by the filtered supernatants of such cultures; adjuvant-soluble factors are therefore involved in the phenomena of adherent, T- and B-cell cooperation required for the adjuvanticity of Brucella fractions.
Insights
Two Brucella fractions act as in vitro adjuvants, enhancing immune responses to sheep red blood cells. These fractions exhibit both general immune activation and specific adjuvant effects, with distinct dose and cellular requirements.
Area of Science:
- Immunology
- Microbiology
Background:
- Brucella fractions are known to modulate immune responses.
- Understanding adjuvant mechanisms is crucial for vaccine development.
Purpose of the Study:
- To investigate the adjuvant properties of two Brucella fractions (PI and SF) in vitro.
- To differentiate between the polyclonal activation and specific adjuvanticity of these fractions.
Main Methods:
- Mishell and Dutton-type cultures using B6/DB F1 mouse spleen cells.
- Assessment of direct anti-sheep erythrocyte plaque-forming cell (PFC) responses.
- Analysis of dose-response and cellular requirements (T-cells, adherent cells).
Main Results:
- Both PI and SF fractions significantly enhanced anti-sheep erythrocyte PFC.
- Polyclonal activation required high adjuvant doses and was T-cell independent.
- Specific adjuvanticity required lower doses and was T-cell and adherent-cell dependent.
- Adjuvant activity could be transferred via stimulated adherent cells or their supernatants, indicating soluble factors.
Conclusions:
- Brucella fractions PI and SF function as in vitro adjuvants.
- Polyclonal activation and specific adjuvanticity are dissociable functions with distinct requirements.
- Soluble factors released by adherent cells mediate the cooperative immune effects of these Brucella fractions.