Table II.

Identifying the pMHC threshold for negative selection and regulatory T-cell generation

Amounts injected:	1 μg
% entering thymus:	0.25%
apmol HEL in thymus:	0.17 pmol
Molecules HEL in thymus:	1011 molecules
bAssume 10% uptake:	1010 molecules
cEfficiency of processing:	0.1% of uptake
dNumber of pMHC:	107
eEstimated number of 48-62 complexes/DC:	25-250 /DC

	*f pMHC/DC
	T reg induction		Negative selection
	Amts	pMHC/DC	Amts	pMHC/DC
3A9	1 μg	25-250	5 μg	125-1250
gLB11	5 μg	0.1-1	30 μg	3-30

Estimates for the number of pMHC complexes that mediate negative selection versus Treg generation in 3A9 and LB11.3 mice.

^aThe calculation of pmol of HEL per thymus is based on data showing that 0.25% of the injected HEL enters the thymus (Figure 1A).

^b10% of the injected HEL is taken up by thymic DC and

^c0.1% of that material is processed to peptide (53).

^dThe number of pMHC complexes generated in the thymus are estimated assuming that

^eOur estimate of pMHC/DC is based on FACS data showing that 10⁵-10⁶ DC are recovered from a B10.BR thymi and 40% of those DCs are positive for HEL (Table I).

^fOur estimate of pMHC/DC is based on FACS data showing that 10⁵-10⁶ DC are recovered from a B10.BR thymi and 40% of those DCs are positive for HEL (Table I).

^gEstimates for LB11.3 assume 250-fold difference in presentation of HEL48-62 versus HEL20-35 based on experimental data (36).

^*A comparison is shown of the HEL doses that marked the thresholds for negative selection and Treg induction in 3A9 and LB11.3 mice.