Maturation of Lymphocyte Immunophenotypes and Memory T Helper Cell Differentiation During Development in Mice

Abstract

The goal of this study was to systematically investigate the ontogeny of lymphoid populations throughout postnatal development. In CD-1 mice, peak lymphocyte numbers occurred in blood on postnatal day 10 (dl0) including those for natural killers (NKI.1), B cells (CD19), T helper (CD3CD4), naive T helper (CD4CD62LpSCD441w), memory T helper (CD4CD62LnegcD44high), and T cytotoxic (CD3CD8) cells. As percent of total lymphocytes, peaks were achieved by d 10 for all T helper subtypes but not B cells which declined to a nadir. In spleen, lymphocyte numbers increased exponentially after d l0. Proportionately, NK and T cells peaked on dl0, declined by d20, and increased 2-3-fold by d45. Naive T cells constituted the majority of lymphocytes during development while memory cells gained to 2.2% (blood) and 12 % (spleen) by d20. C57BL/6 mice had similar profiles except that the B cell nadir and T cell subset peaks were at d5. Peripheralization of critical numbers of lymphocytes by d l0, and importantly, development of a repertoire of memory cells by d20, may define immune response capabilities that close the period of immaturity for the neonate.

Ontogenic Development of Th1 and Th2 Cytokine Capabilities in Random Bred Mice

“…In contrast, in the total unsorted cell cultures this ratio could be calculated for B cells to CD3 cells only. The B:T cell ratios were: 11:1, 8:1, 4:1, 11:1, 4:1, 2:1 for 3-, 4-, 5-, 10-, 20-, and 45-day old pups, respectively (data obtained in a parallel immunophenotyping study; Fagoaga et al, 2001). Indeed, APC:T cell ratios are higher when monocytes and dendritic cells are taken into account.…”

“…Before day 5, there are very few memory cells in spleen, while adult spleens contain manyfold greater numbers (Fagoaga et al, 2001). Memory cells migrate to spleen after down-regulating CD62L expression (Forsthuber et al, 1996), and have increased capacity to produce Th1 and Th2 cytokines compared to naïve cells (Bradley et al, 1992).…”

“…In neonates, memory cells are generated in response to foreign and self (peripheral) antigens (post-thymic education; Alferink et al, 1998). In a previous study (Fagoaga et al, 2001), high thymic output of naïve T cells was observed between days 3 and 10. Thus, these early thymic naïve emigrants may be involved in self-antigen recognition and tolerization, an activity that would induce changes in cytokine responses.…”

“…Also novel to these culture experiments was the preservation of age-specific Th-to-APC ratios by culturing uncorrupted mixed-cell preparations. This decision was a logical extension of our immunophenotyping data (Fagoaga et al, 2001) illuminating dynamic changes occurring in neonatal spleen cell populations. Without consideration of cell proportions, erroneous assessment of functional capabilities by sorted, isolated cells in culture is probable.…”

Photoperiod, Reproduction, and Immunity in Select Strains of Inbred Mice

“…Whole blood and dispersed splenocytes were processed by flow cytometry to identify immunophenotypes according to previously described standard laboratory practices (Fagoaga et al, 2001). Leukocytes were manually counted (Unopette Cell Counting System, Fisher Scientific, Tustin, CA), and then lymphocyte preparations were labeled with murine-specific fluorochrome--tagged monoclonal antibodies (PharMingen, San Diego, CA).…”