FcRγ−/− C3−/− mice were generated by Rapamycin cell line breeding in our animal facility. Breeding pairs of MD4 and C3−/− mice were obtained from Dr. Christian Kurts (Bonn) and from Dr. Admar Verschoor (Munich), respectively. Mice were bred and kept in our animal facility under specific pathogen-free conditions. Animal care and use was approved by the Regierungspräsidium Freiburg. LCMV Armstrong, LCMV WE, and LCMV Docile were propagated on baby hamster kidney cells, L929, and Madin Darby canine kidney cells, respectively. Viral titers were determined by

standard focus-forming assay using serial dilutions of tissue homogenate and MC57G fibrosarcoma cells as described [55]. Mice were infected i.v. with 200 PFU of the respective virus strain. MC57G fibrosarcoma or B16 melanoma cells were infected with MK-2206 mw LCMV Docile in vitro with multiplicity of infection (m.o.i.) of 0.01. Cells were harvested after 48–72 hours. LCMV immune serum was collected from 8–10 weeks old SWISS or NMRI mice 20 days after infection with 200 PFU LCMV Docile using BD Microtainer SST Tubes (BD Bioscience). Sera were used as pools from 20–40 mice and tested for LCMV titers and virus neutralizing activity using focus-forming assay as described [55]. Only LCMV immune sera free of infectious virus were used. Normal mouse serum was purchased from

Harlan Laboratories. Mice were treated (i.p.) with 500 μL of immune or normal serum at day 1 after infection with 200 PFU LCMV-Docile. IgG from LCMV immune serum was purified using HiTrap Protein G HP 1 mL columns (GE Healthcare) with the Amersham Biosciences UPC-900 FPLC. Purified IgG from normal mouse serum was purchased from Innovative Research. Mice were treated (i.p.) with 3.3 mg purified IgG in 0.4 mL of PBS. LCMV NP specific mAbs were derived from the mouse IgG2a secreting CYTH4 hybridoma KL53 [23] or from the rat IgG hybridoma VL-4 [55]. Mice were given (i.p.)

500 μg KL53 mAbs (ascites fluid or concentrated hybridoma supernatant) or 700 μg purified VL4 mAbs (BioXcell). For CD8+ T-cell depletion, mice were treated (i.p.) with 400 μg anti-CD8 mAbs (YTS169) at d1 and d2 before infection. The following mAbs were obtained from BD Biosciences or eBiosience: anti-CD8α (53–6.7), anti-KLRG1 (2F1), anti-PD1 (J43), anti-2B4 (ebio244F4). LCMV GP and LCMV NP on the surface of infected cells were stained with primary mAb KL25 [56] or mAb KL53 [23] derived from hybridoma supernatant followed by anti-mouse IgG-Alexa647 (Invitrogen) as a secondary Ab. Samples were analyzed using FACSCalibur or LSRFortessa flow cytometer (both BD Biosciences) and FlowJo software (Tree star). For detection of LCMV-specific IgG, 96-well high-binding ELISA plates (Greiner bio-one) were coated with 100 μL per well rabbit anti-LCMV immune serum diluted 1:2000 in PBS at 4°C overnight.