At the first indication of an "HTLA" antibody using the common characteristics described previously, there are several courses of action you can take. The most logical one is to perform an antibody titration to determine if it fits the characteristics of high titer and low avidity.
Suppose you ran several phenotypically similar panel cells as suggested in the previous step. In that case, one of the cells that was reactive is an ideal choice for the antibody titration rather than choosing a random cell from the initial panel because it is less likely that if there is a clinically significant antibody in the plasma it will react with that cell.
In Table 2 below, you can see the titration results when performed with cell number 3 from the phenotypically similar select cell panel run in the previous step. Note that the most dilute plasma that reacted with the panel cell is relatively high, but the reaction strength is consistently weak through several dilutions. This fits with the high titer and low avidity characteristics that these types of antibodies are named for.
Table 2. Antibody Titration of Cell #3 from Phenotypically Similar Select Cell Panel.| Cell Titered | 1:1 | 1:2 | 1:4 | 1:8 | 1:16 | 1:32 | 1:64 | 1:128 | 1:256 | 1:512 | 1:1024 | 1:2048 |
| Cell #3 | 1+ | 1+ | 1+ | w+ | w+ | w+ | 0√ | 0√ | 0√ | 0√ | 0√ | 0√ |
If the antibody titration testing gave you a different pattern of reactivity, or didn't titer at all, that would suggest an antibody of another specificity rather than an "HTLA" antibody, making this a useful tool for investigation.
