C3H mice (H-2 k ) and Balb/c mice (H-2 d ) were infected with LCM virus to gener

Question

C3H mice (H-2k) and Balb/c mice (H-2d) were infected with LCM virus to generate cytotoxic T cells. Spleen cells from these mice were removed and tested for their cytotoxic ability. In this assay the target cells were labelled with 51Cr and this radioactive element was released when the cells were lysed. In order to follow the activity of this reaction various ratios of killer to target cells are used.

a. based on Figure 1 which cells were vulnerable to attack by the C3H LCMV activated killer T cells and which molecules were recognized?

b. based on Figure 1 which cells were vulnerable to attack by the Balb/c LCMV activated killer T cells and which molecules were recognized?

100 Fig. 1 Killing of LCMV-infected L-cel transformants by spleen cells from LCMV-infected C3H (H-2*)and BALB/c(H-2") mice Groups of two 6-8-week-old C3H/Bang and BALB/c mice were infected intraperitoneally with 2.5 x 102 plaque-forming units of the Armstrong strain of LCMV 7 days before cytotoxic assay. Spleens were removed and single cell suspensions prepared. L-cell transformants were grown in hypoxanthine-aminopterin- thymidine medium and Nulli-2A teratocarcinoma cells in Dul becco's modified Eagle's medium supplemented with 10% fetal calf serum (FCS). The presence of Ld and Kd molecules on the transformants was monitored by radioimmunoassay using mono- clonal antibodies as described previously. Target cells were infec- ted with LCMV 40 h before cytotoxicity assay at a multiplicity of infection of 0.5, then trypsinized, washed, and labelled for 1 h at 37°C with 200 ?C," Cr in 0.5 ml RPMI supplemented with 10% FCS and 20mM HEPES. After washing, 10* target cells were mixed in triplicates in microtitre plates with varying numbers of effector spleen cells in a total volume of 200 ?1. Plates were incubated at 37 °C, 5% CO2 for 4 h, then centrifuged and 100 l of the supernatant were removed and counted in a y-counter Per cent specific lysis was calculated according to the for- mula: c.p.m.exp c.p.m.spon/c.p.m.max C.p.m.spon X 100, where c.p.m.spon (spontaneous) and c.p.m.max (maximum) were deter- mined in cultures containing medium or detergent, respectively; cp.m.exp, C.p.m. (experimental). The se.m. never exceeded 5% The figure shows results for spleen effector cells from a, LCMV infected C3H/Bang mice, and b, LCMV-infected BALB/c mice. Target cells: ., 8-5 (La)-LCMV; ?, 8-5, uninfected; ? L-k+- LCMV: A, L-tk, uninfected;, K7-65 (Kd)-LCMV; O, K7-65, uninfected; , Nulli-2A-LCMV; O, Nulli-2A, uninfected. 50 100:1 50:1 25:1 12.5:1 100 50 6023 1001 soi 25:1 0.5:1

Explanation / Answer

a. 8-5 cells, L-tk+ cell and K7-65 cells , all infected with LCMV were vulnerable to attack by the C3H LCMV activated killer T cells and both Ld and Kd molecules were recognized.

b. 8-5 cells infected with LCMV were vulnerable to attack by the Balb/c LCMV activated killer T cells and only Ld  molecules were recognized.

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