The heat stable antigen (CD24) is not required for the generation of CD4+ effector and memory T cells by dendritic cells in vivo
Introduction
The sensitization of naı̈ve T cells is a complex event involving several cascades of transduction initiated by the engagement of antigenic receptor and costimulatory molecules. Among the population of antigen-presenting cells, dendritic cells (DCs) display the unique capacity to optimally sensitize naive T cells in vitro and in vivo. The potency of DCs has been attributed to their capacity to increase expression of CD80/CD86 costimulatory molecules “upon minimal stimulation” [1], a property which has not been ascribed to B lymphocytes and macrophages.
Other costimulatory molecules have been identified that are required for optimal activation of naı̈ve and/or primed T cells [2]. Among them, HSA or CD24 displays distinctive features: it is extremely small, containing an estimated 30 amino acids after removal of signal peptide and displacement of its C-terminal region. The maturation of HSA from a peptide to proteins with apparent masses ranging from 35 to 60 kDa appears to be the result of extensive glycosylation at multiple N- and O-linked sites. The sizes of the HSA molecule vary considerably among hemopoietic cells types [3], [4].
Several reports have established that CD24 on activated B cells [5], [6], macrophages [7], and epidermal Langerhans’ cells [8] play important roles for T-cell activation. Moreover, previous studies using mice with targeted mutation of CD24 indicate that its costimulatory activity is essential when the CD28-mediated costimulatory pathway in blocked [9].
However, the cellular basis for CD24-mediated costimulatory in vivo has not been determined. In this study, we compared the functional properties of HSA-competent or deficient DC in vivo and found that this costimulatory molecule is not required for the differentiation of effector and memory CD4+ T lymphocytes by adoptive transfer of antigen-pulsed DCs.
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Mice
BALB/c and C57BL/6 mice were purchased from Harlan Nederland (Horst, The Netherlands). CD24 knock out mice were generated on a C57BL/6 background as previously described [9]. OT-II mice, transgenic for αβ-TCR reactive with the I-Ab—restricted 323–339 peptide of ovalbumin were kindly provided by Dr. Patrice Dubois (GlaxoSmithKline, Rixensart, Belgium) with the permission of Dr. William R. Heath (Immunology Division, the Walter and Eliza Hall Institute, Post Office Royal Melbourne Hospital,
Phenotypic analysis of splenic DC from wild-type and CD24 KO mice
We purified splenic DC from WT or CD24−/− mice and analysed their expression of CD11c, MHC and costimulatory molecules. DCs were enriched for N418+ cells by magnetic cell sorting and cultured overnight with GM-CSF. During the culture period, they undergo maturation and upregulate MHC class II and B7 expression, as shown previously [12], [14]. The data in Fig. 1 show that most cells in the DC-enriched population of either strain express similar levels of CD11c, CD80, CD86, H-2Kb and I-Ab
Discussion
The findings presented here suggest that CD24, a costimulatory molecule constitutively expressed on DCs, is not required for CD4 T-cell priming or induction of memory activity by these antigen-presenting cells in vivo. Expression of B7 molecules on DC conveys full costimulation to naı̈ve and pre-activated CD4 T cells as clonal expansion and IFN-γ production are abrogated by anti-CD80 and anti-CD86 mAbs. Although we cannot rule out the possibility that HSA-competent host cells may present
Acknowledgements
The authors are grateful to Serge Goldman, Didier Blocklet (ULB, Hopital Erasme), Alain Trautman, Patrick Revy (Hopital Cochin, Paris, France) for collaboration and interesting discussions, to Oberdan Leo for review and suggestions, Anna-Sophie Vanherck for help in the generation of BMDCs and to Philippe Veirman for animal care. The Laboratory of Animal Physiology is supported by grants of the FNRS/Télévie, by the P.A.I., by an Action de Recherche Concertée de la Communauté Française, and by
References (29)
- et al.
Curr. Opin. Immunol.
(1999) - et al.
J. Immunol. Methods
(1994) - et al.
Immunity
(1998) - et al.
J. Exp. Med.
(1994) - et al.
J. Leukoc. Biol.
(2001) - et al.
J. Cell Biol.
(1992) - et al.
J. Exp. Med.
(1992) - et al.
J. Immunol.
(1991) - et al.
J. Immunol.
(1996) - et al.
J. Immunol.
(1994)