Supporting Text

Immunocytochemistry. Sections were preincubated in 3 % horse normal serum, 3 % bovine serum albumin, and 0.1 % of Triton X-100 in PBS for 1 hr. The primary antibodies were diluted in 0.05 % Triton X-100 in PBS and were applied overnight. Secondary antibodies included anti-mouse IgG Alexa568 (1:500, Molecular Probes), anti-mouse IgM Alexa568 (1:500, Molecular Probes), and anti-rabbit IgG Alexa488 (1:500, Molecular Probes). The secondary antibodies were diluted in PBS and applied for 3 hr. Sections were washed in PBS and covered with Vectashield (Vector Laboratories). Images were obtained with a Zeiss Axioplan 2 microscope and a SPOT camera, and a Leica TCS SP2 confocal microscope equipped with an Ar 488 laser and HeNe 543 laser lines.