Do most lymphocytes in humans really reside in the gut?

Noninvasive in vivo imaging of CD4 cells in simian-human immunodeficiency virus (SHIV)–infected nonhuman primates

“…Using a value of 30% for the fraction of splenic lymphocytes that are CD4 ϩ cells, 21 one can calculate that the entire human spleen contains approximately 5.3 ϫ 10 11 lymphocytes. Assuming that the spleen contains approximately 15% of the total lymphoid pool, 1,22 we calculate the total body number of lymphocytes to be approximately 3.5 ϫ 10 12 , or approximately 8-fold higher than previously reported. 1,2,22 To attempt to validate these estimates derived from in vivo labeling with the anti-CD4 antibody, we calculated the number of lymphocytes present in the spleen and lymph nodes of the uninfected monkey CH3397 through cell counting analysis of sections of immunohistochemistry stained tissue sections (supplemental data).…”

“…Assuming that the spleen contains approximately 15% of the total lymphoid pool, 1,22 we calculate the total body number of lymphocytes to be approximately 3.5 ϫ 10 12 , or approximately 8-fold higher than previously reported. 1,2,22 To attempt to validate these estimates derived from in vivo labeling with the anti-CD4 antibody, we calculated the number of lymphocytes present in the spleen and lymph nodes of the uninfected monkey CH3397 through cell counting analysis of sections of immunohistochemistry stained tissue sections (supplemental data). By these methods, we calculate a lower estimate for the total number of lymphocytes in the spleen to be 2.9 ϫ 10 11 and, by extrapolation, the total body number of lymphocytes in humans to be 1.9 ϫ 10 12 or approximately 4-fold higher than previously reported.…”

“…This compartment has been reported to represent approximately 2% of total body lymphocytes. 1,2,22 The CD4 T-cell count in the blood is recognized as a major prognostic marker of disease progression. Despite the critical role of CD4 ϩ T cells in host defense, the peripheral blood CD4 ϩ T-cell count appears to predict only up to 30% of the variability in AIDS or death for all causes.…”

“…One implication of these estimates is that, in a healthy subject, the lymphocytes in the blood contribute substantially less to the total lymphocyte pool than the frequently cited 2% value. 1,2,22 If one assumes a total blood volume of 5 L in a 70-kg adult human, a peripheral blood lymphocyte count of 2000 cells/L, and that 50% of these cells are CD4 ϩ T cells, the total number of lymphocytes in the blood would be calculated to be 10 ϫ 10 9 , 1 and the number of CD4 ϩ T cells 5 ϫ 10 9 . Given the aforementioned range of 1.9 ϫ 10 12 to 3.5 ϫ 10 12 lymphocytes in the body, the blood would contribute between 0.3% and 0.5% to the total pool of lymphocytes.…”

News & Highlights

“…However, Ganusov and De Boer have challenged this view. 1 Pabst and colleagues, in responding to Ganusov and De Boer concerning antibody-secreting cells, make a persuasive case that indeed 70% of these cells in the body reside in the gut lamina propria. 2 However, they are reluctant to make a similar case for T cells and non-antibody-secreting B cells, mainly because good data are not available.…”