Nai tl là gì? Các công bố khoa học về Nai tl

In a depleted lymphoid compartment, naive T cells begin a slow proliferation that is independent of cognate antigen yet requires recognition of major histocompatibility complex–bound self-peptides. We have followed the phenotypic and functional changes that occur when naive CD8+ T cells undergo this type of expansion in a lymphopenic environment. Naive T cells undergoing homeostasis-driven proliferation convert to a phenotypic and functional state similar to that of memory T cells, yet distinct from antigen-activated effector T cells. Naive T cells dividing in a lymphopenic host upregulate CD44, CD122 (interleukin 2 receptor β) and Ly6C expression, acquire the ability to rapidly secrete interferon γ, and become cytotoxic effectors when stimulated with cognate antigen. The conversion of naive T cells to cells masquerading as memory cells in response to a homeostatic signal does not represent an irreversible differentiation. Once the cellularity of the lymphoid compartment is restored and the T cells cease their division, they regain the functional and phenotypic characteristics of naive T cells. Thus, homeostasis-driven proliferation provides a thymus-independent mechanism for restoration of the naive compartment after a loss of T cells.

The developmental requirements for immunological memory, a central feature of adaptive immune responses, is largely obscure. We show that as naive CD8 T cells undergo homeostasis-driven proliferation in lymphopenic mice in the absence of overt antigenic stimulation, they progressively acquire phenotypic and functional characteristics of antigen-induced memory CD8 T cells. Thus, the homeostasis-induced memory CD8 T cells express typical memory cell markers, lyse target cells directly in vitro and in vivo, respond to lower doses of antigen than naive cells, and secrete interferon γ faster upon restimulation. Like antigen-induced memory T cell differentiation, the homeostasis-driven process requires T cell proliferation and, initially, the presence of appropriate restricting major histocompatibility complexes, but it differs by occurring without effector cell formation and without requiring interleukin 2 or costimulation via CD28. These findings define repetitive cell division plus T cell receptor ligation as the basic requirements for naive to memory T cell differentiation.

Complement receptor 2–negative (CR2/CD21−) B cells have been found enriched in patients with autoimmune diseases and in common variable immunodeficiency (CVID) patients who are prone to autoimmunity. However, the physiology of CD21−/lo B cells remains poorly characterized. We found that some rheumatoid arthritis (RA) patients also display an increased frequency of CD21−/lo B cells in their blood. A majority of CD21−/lo B cells from RA and CVID patients expressed germline autoreactive antibodies, which recognized nuclear and cytoplasmic structures. In addition, these B cells were unable to induce calcium flux, become activated, or proliferate in response to B-cell receptor and/or CD40 triggering, suggesting that these autoreactive B cells may be anergic. Moreover, gene array analyses of CD21−/lo B cells revealed molecules specifically expressed in these B cells and that are likely to induce their unresponsive stage. Thus, CD21−/lo B cells contain mostly autoreactive unresponsive clones, which express a specific set of molecules that may represent new biomarkers to identify anergic B cells in humans.

This study provided validity evidence for the Godin-Shephard Leisure-Time Physical Activity Questionnaire (GSLTPAQ) to classify respondents into active and insufficiently active categories. Members of a fitness center [45 women and 55 men; mean ( SD) age = 45.5 (10.6) yr.] completed the questionnaire. Using only moderate and strenuous scores, those with a leisure score index ≥ 24 were classified as active; those with a score ≤ 23 were classified as insufficiently active. VO₂max, percentage of body fat, and electronic records of fitness center attendance were the validation variables. In a visit to the fitness center, participants completed the GSLTPAQ and a certified exercise specialist performed a physical fitness evaluation. A multivariate analysis of covariance (MANCOVA) indicated the group of respondents classified as active had higher VO₂max and lower percentage of body fat than the group of respondents classified as insufficiently active. An analysis of covariance (ANCOVA) indicated the group of respondents classified as active had higher electronic records of fitness center attendance than the group of respondents classified as insufficiently active. Therefore, these pieces of validity evidence support the use of the questionnaire's classification system among healthy adults.