The CD5 ectodomain interacts with conserved fungal cell wall components and protects from zymosan-induced septic shock-like syndrome.
The CD5 lymphocyte surface receptor is a group B member of the ancient and highly conserved scavenger receptor cysteine-rich superfamily. CD5 is expressed on mature T and B1a cells, where it is known to modulate lymphocyte activation and/or differentiation processes. Recently, the interaction of a few group B SRCR members (CD6, Spalpha, and DMBT1) with conserved microbial structures has been reported. Protein binding assays presented herein indicate that the CD5 ectodomain binds to and aggregates fungal cells (Schizosaccharomyces pombe, Candida albicans, and Cryptococcus neoformans) but not to Gram-negative (Escherichia coli) or Gram-positive (Staphylococcus aureus) bacteria. Accordingly, the CD5 ectodomain binds to zymosan but not to purified bacterial cell wall constituents (LPS, lipotheicoic acid, or peptidoglycan), and such binding is specifically competed by beta-glucan but not by mannan. The K(d) of the rshCD5/(1-->3)-beta-d-glucan phosphate interaction is 3.7 +/- 0.2 nM as calculated from tryptophan fluorescence data analysis of free and bound rshCD5. Moreover, zymosan binds to membrane-bound CD5, and this induces both MAPK activation and cytokine release. In vivo validation of the fungal binding properties of the CD5 ectodomain is deduced from its protective effect in a mouse model of zymosan-induced septic shock-like syndrome. In conclusion, the present results indicate that the CD5 lymphocyte receptor may sense the presence of conserved fungal components [namely, (1-->3)-beta-d-glucans] and support the therapeutic potential of soluble CD5 forms in fungal sepsis.
Vera
Jorge
J
Servei d'Immunologia, Hospital Clínic de Barcelona, Institut d'Investigacions Biomèdiques August Pi i Sunyer, 08036 Barcelona, Spain.
Fenutría
Rafael
R
Cañadas
Olga
O
Figueras
Maite
M
Mota
Rubén
R
Sarrias
Maria-Rosa
MR
Williams
David L
DL
Casals
Cristina
C
Yelamos
José
J
Lozano
Francisco
F
D000818:Animals; D001419:Bacteria / Q000378:metabolism; D018956:CD5 Antigens / Q000737:chemistry / Q000378:metabolism*; D002176:Candida albicans / Q000166:cytology / Q000378:metabolism*; D002460:Cell Line; D002473:Cell Wall / Q000378:metabolism*; D003455:Cryptococcus neoformans / Q000166:cytology / Q000378:metabolism*; D016207:Cytokines / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D006801:Humans; D020935:MAP Kinase Signaling System; D008297:Male; D051379:Mice; D012568:Schizosaccharomyces / Q000166:cytology / Q000378:metabolism*; D012772:Shock, Septic / Q000139:chemically induced / Q000382:microbiology / Q000517:prevention & control*; D015054:Zymosan / Q000633:toxicity*
D018956:CD5 Antigens; D016207:Cytokines; D015054:Zymosan