Table 1.
Parameters Governing Homeostasis of Circulating Follicular Mature B Cells and Germinal Center B Cells in the Spleen ansd Lymph Nodes
| Population | Parameter | Estimate and 95% CI | |||
|---|---|---|---|---|---|
| FM B cells | Daily influx from T1 (as % of subset) at age 75 days | 2.9 | (2.5, 3.4) | ||
| at age 300 days | 2.1 | (1.8, 2.4) | |||
| Daily influx from T1 at age 75 days (cells/day ×10−6) | 0.87 | (0.74, 1.0) | |||
| at age 300 days | 0.85 | (0.73, 0.99) | |||
| Mean residence time at age 75 days (d) | 35 | (29, 42) | |||
| at age 300 days (d) | 42 | (35, 50) | |||
| Time taken for mean residence time to double (months) | 27 | (15, 115) | |||
| Mean clonal lifespan at age 75 days (d) | 41 | (33, 50) | |||
| at age 300 days (d) | 51 | (43, 61) | |||
| Mean inter-division time (d) | 400 | (110, 1200) | |||
| Ki67hi → Ki67lo transit time (d) | 5.8 | (4.4, 7.2) | |||
| GC B cells | Daily influx from T2 (as % of subset) at age 75 days | 5.0 | (3.3, 7.1) | ||
| (Spleen) | at age 300 days | 3.8 | (2.4, 5.7) | ||
| Mean residence time (d) | 0.55 | (0.41, 0.73) | |||
| Mean clonal lifespan (d) | 29 | (23, 35) | |||
| Mean inter-division time (d) | 0.56 | (0.41, 0.75) | |||
| Time taken for per capita rate of influx to double (d) | 230 | (120, 680) | |||
| Ki67hi → Ki67lo transit time (d) | 5.5 | (4.1, 7.1) | |||
| Transient Subset | Persistent Subset | ||||
| GC B cells | Daily influx from FM B cells (% of subset) at age 75 days | 0.63 | (0.08, 2.1) | 2.1 | (1.2, 3.4) |
| (Lymph nodes) | at age 300 days | 0.36 | (0.03, 1.6) | 1.8 | (1.0, 2.7) |
| Mean residence time (d) | 0.51 | (0.35, 0.69) | 0.73 | (0.42, 0.74) | |
| Mean clonal lifespan (d) | 21 | (1, 58) | 140 | (50, 550) | |
| Mean inter-division time (d) | 0.58 | (0.43, 0.75) | 0.73 | (0.53, 1.4) | |
| Proportion of total GC B cells at age 75 days | 0.23 | (0.06, 0.39) | 0.77 | (0.61, 0.94) | |
| at age 300 days | 0.16 | (0.03, 0.37) | 0.83 | (0.63, 0.97) | |
| Ki67hi → Ki67lo transit time (d) | 5.9 | (4.6, 7.3) | 5.9 | (4.6, 7.3) | |
95% credible intervals were estimated by taking the 2.5 and 97.5 percentiles of the posterior probability distributions of the parameter values. We inferred that the expected residence time of FM B cells (that is, the mean time until their loss or onward differentiation) increases with host age. For splenic GC B cells, the rate of influx of new cells into the compartment from T2 precursors increases with host age. We infer that lymph node GC B cells derive from FM B cells and comprise at least two subpopulations with different rates of division and loss. Both populations are assumed to share the same Ki67 lifetime.