ACTIVATION OF CYTOKINE GENES DURING PRIMARY AND ANAMNESTIC IMMUNE-RESPONSE TO INACTIVATED CANDIDA-ALBICANS

Recent evidence suggests that after repeated stimulations with inactiv ated C. albicans (CA) cells, CD2F1 mice respond with a cytokine patter n typical of T-helper 1 (Th1) subset development. The purpose of this study was to analyse the sequence of immunological events which, soon after priming mice with CA, lead to the development of primary and ana mnestic response. A comprehensive kinetics analysis of cytokine mRNA e xpression was performed by Northern blot assay, in peritoneal exudate cells (PEG), at different phases of immune response to CA: after primi ng (one i.p. injection of 2 x 10(7) CA cells/mouse), during developmen t of the primary immune response (five progressive CA i.p. injections over a 2-week period) and in the anamnestic response (CA booster 30 da ys after the primary response). In vitro assays were performed 2 and 2 4 hr after every CA stimulation. The response to CA priming was charac terized by an early and high expression of interleukin-2 (IL-2) and IL -1 beta mRNAs. At 24 hr, IL-2 mRNA was still at a high level, while IL -1 beta had greatly decreased. A weak expression of IL-10 was only ind uced at 2 hr, whereas IL-12 p40 subunit, interferon-gamma (IFN-gamma), IL-4 and IL-5 mRNAs were undetectable. In this phase no in vitro prol iferative response of PEC to CA was observed, whereas a significant na tural killer (NK) activity was induced. From the second CG injection, the IFN-gamma mRNA was already induced at 2 hr. Its expression level i ncreased progressively with the number of CA injections persisting up to 24 hr after the fifth stimulation. A progressive increase of IL-2 m RNA expression was also induced whereas IL-1 beta and IL-10 mRNAs were always transiently expressed at 2 hr at levels similar to those obser ved after the priming. IL-12 p40 subunit, IL-4 and IL-5 mRNAs were nev er detectable. The expression of this selected cytokine pattern typica l of Th1 response was correlated with the development of CA-specific T lymphocytes as confirmed by the in vitro proliferative response of CA -5d-induced PEC to CA. NK activity also increased progressively with t he number of CA injections and after the fifth stimulation lymphokine- activated killer (LAK) activity was also induced. The anamnestic respo nse to CA was characterized by a very quick induction of high levels o f IL-2, IFN-gamma and IL-1 beta mRNAs. IL-2 and IFN-gamma mRNAs remain ed high up to 24 hr while IL-1 beta mRNA decreased strongly. A weak, t ransient expression of IL-10 mRNA was induced at 2 hr whereas the IL-1 2 p40 subunit, IL-4 and IL-5 mRNAs were not detectable. The presence o f CA-specific memory lymphocytes was confirmed by the in vitro specifi c proliferative response of PEC to CA. CA booster caused also a very r apid and high level of NK/LAK activation. In conclusion, these results indicate that CA is able to progressively trigger differentiation of the Th1 subset which develops in the absence of IL-12, and that Th mem ory cells retain the same selected Th1 cytokine profile developed in t he primary immune response.