Cells challenged with higher doses of antigen (>10 pg DNP-HSA) delivered as single doses achieved significant β-hexosaminidase release. The black Selleck Fer-1 bar in Fig. 1A (1 ng DNP) represents the optimal triggering dose of 1 ng DNP-HSA used as target dose for rapid desensitization

to 1 ng of DNP-HSA (DNP Des). The release obtained with single-dose additions in Fig. 1A was compared to that obtained with doses added sequentially, following every step of the desensitization protocol (see Fig. 1B, white bars). White bars represent β-hexosaminidase release at each particular point in the cumulative sequence of antigen additions. A maximum of 10% β-hexosaminidase release was achieved at all points in the sequence, showing that the desensitization process did not induce a slow release of mediators. To determine whether there was a threshold dose that initiated hypo-responsiveness, replicate samples were used, and at each particular point in the sequence of antigen additions, cells were also challenged with a triggering dose of 1 ng DNP-HSA (see Fig. 1B, gray bars). Response to the triggering dose declined with increasing number

of sequential selleck inhibitor doses. The greatest hypo-responsiveness was achieved with the highest number of sequential additions (11, in Fig. 1B), indicating that hypo-responsiveness was not stabilized until the end of the desensitization protocol. To test whether cells’ hypo-responsiveness achieved with rapid desensitization to

1 ng DNP-HSA could be overcome with higher challenging doses, we analyzed the response of desensitized cells to activating doses of 1, 2, 3, 4 and 5 ng of DNP-HSA. Up to five-fold increase in challenging dose did not reverse desensitization (see Fig. 1C). The protocol was effective when increasing the target dose to 5 and 10 ng, with the same number of steps, time between steps and starting dose (1/1000 the target dose), but less inhibition of β-hexosaminidase release was observed (see Fig. 1D). Cells desensitized to 1 ng DNP-HSA showed a 75% inhibition whereas cells desensitized to 5 and 10 ng DNP-HSA had a 65 and 41% inhibition of β-hexosaminidase release, respectively. BMMCs sensitized with anti-DNP IgE or anti-OVA IgE were rapid-desensitized STK38 as per the protocol presented in Table 1. In both DNP and OVA systems, we measured the release of β-hexosaminidase when antigen was delivered as a single dose (1 ng DNP-HSA/10 ng OVA, black bars in Fig. 2A) or when antigen was delivered following the rapid desensitization protocol (white bars in Fig. 2A). Cells desensitized to 1 ng DNP-HSA and 10 ng OVA showed a 78 and 71% inhibition of β-hexosaminidase, respectively. Exocytosis of pre-formed mediators from granules cannot occur without external calcium entry.