volume target, effector:target ratios?, volume cells

Question

You will calculate the concentrations of the components required for a chromium release cytotoxicity assay. Target cells are labelled with radioactive chromium and incubated with CD8 effector cells for 6 hours. The release of the radioactivity can be measured as counts per minute (cpm) and the amount of target cell killing calculated.

Your assay has radioactively labelled tumour cell targets and you will add your killer cells, called effectors, to the targets.

The effector cells will be added to the target cells in increasing numbers to give effector:target ratios of 40:1, 20:1, 10:1 and 5:1.

Part 1

a) You have radioactively labelled target cells at a concentration of 2 x 10⁵ per ml. You need 1 x 10⁴ cells in each well, which will be constant, for your assay.

Volume of target cells required = (Answer) μl

b) As you have 1 x 10⁴ target cells, how many effector cells will you need for each of the following effector:target ratios?

40:1 = (Answer) x 10(^Answer) cells

20:1 = (Answer) x 10(^Answer) cells

10:1 = (Answer) x 10(^Answer) cells

5:1 = (Answer) x 10(^Answer) cells

c) Your effector cells are in a suspension at a concentration of 1 x 10⁶ per ml. What volume of cells will you need to obtain the required number of effectors for the effector:target ratios?

40:1 = (Answer) μl

20:1 = (Answer) μl

10:1 = (Answer) μl

5:1 = (Answer) μl

****the empty (answer) boxes which need to be answered****

Answer 1

Hello Rek,

This should help you out.

1. For question a.) It says that the concentration of the cells is 2*10⁵ cells per ml. To make calculations easier convert ml to microliters. So you essentially have 2*10⁵ cells per 1000µl. Now calculate how many cells you have per µl of sample.

i.e 1000µl has 2*10⁵ cells so how much does 1µl have. its a straight forward calculation.

After you have figured out how many cells per ul you have available from the previous calculation you can easily determine the volume required to get 1*10⁴ cells or 10000 cells. Essentially dividing 10000 using the value you get from the above calculation

1. Question b. is very straight forward. The ratios given are Effector cells: Target cell. You already know that Target cell is 1*10⁴ so if you go by for example ratio 40:1[Effector:Target] all you need to do is to multiply corresponding effector number value with 1*10⁴ to figure out number of effector cells needed
2. Question c. Once you figure out values of effector cell for each condition you will be easily able to determine the volume by dividing the corresponding values for each condition with the given concentration 1*10⁶ to get the volumes

i.e Number of cells calculated from question b/ 1*10⁶

Please feel free to contact me if you have any other questions