Apoptosis

Apoptosis + Necrosis.
Human intermediate filament protein cytokeratin 18 (K18).
Released from human epithelial cells.

serum, plasma (EDTA, Heparin, Citrate) and cell (epithelial cell

Store samples at 2 – 8 °C up to 4 hours. For longer
periods, store samples frozen at -20 °or lower.
Samples can be freeze-thawed without loss of activity it is recommended that repeated freeze thawing should be avoided.

Median level 264 U/L with a range between 136 – 480 U/L.
95th percentile was 413 U/L.
Total soluble K18 (uncleaved and cleaved Keratin 18 representing total cell death (necrosis and apoptosis) was measured in 200 apparently normal Swedish blood donors. Male and female values showed a similar distribution and no age dependency. Based on the distribution the cut-off value for elevated K18 has been set at > 450 U/L.

Human , primates, bovine

The assay uses two monoclonal antibodies directed to epitopes in the
284 – 396 region of the K18 protein. Soluble full length K18 as well as K18 fragments and protein complexes that expose these epitopes will be detected by the assay.

The Standard provided with the kit contains recombinant material which is not comparable to the fragment measured in the sample and is not adequate for spiking recovery tests. The recovery for the recombinant K18 protein fragment observed in human serum/plasma will be higher than expected.

Recovery for human sera when diluted 1:2 in M65 Standard A (0 Units/L): 126 % (average) and 116 – 139 % (range).
Recovery for human sera when diluted 1:1 to 1:10 in the M65 Sample Dilution Buffer: 106 % (average and 100 – 117 % (range).

No high dose “hook effect” occurs before 70 000 U/L.

Quantitative measurement of total soluble cytokeratin 18 (K18) released from dead cells (necrotic and apoptotic). The cells or tissues should be of human epithelial origin (e.g. kidney, gut, colon, lung or liver) expressing K18.

The M65® ELISA can be combined with the M30-Apoptosense® ELISA (PEVIVA Prod. No. 10010) for determination of cell death mode (apoptosis versus necrosis). Death mode can be determined in vitro and in serum from cancer patients (Kramer et al., Cancer Res. 2004).