Abstract
Clinically isolated syndrome (CIS) is the earliest clinical episode in multiple sclerosis (MS). Low environmental exposure to UV radiation is implicated in risk of developing MS, and therefore, narrowband UVB phototherapy might delay progression to MS in people with CIS. Twenty individuals with CIS were recruited, and half were randomised to receive 24 sessions of narrowband UVB phototherapy over a period of 8 weeks. Here, the effects of narrowband UVB phototherapy on the frequencies of circulating immune cells and immunoglobulin levels after phototherapy are reported. Peripheral blood samples for all participants were collected at baseline, and 1, 2, 3, 6 and 12 months after enrolment. An extensive panel of leukocyte populations, including subsets of T cells, B cells, monocytes, dendritic cells, and natural killer cells were examined in phototherapy-treated and control participants, and immunoglobulin levels measured in serum. There were significant short-term increases in the frequency of naïve B cells, intermediate monocytes, and fraction III FoxP3+ T regulatory cells, and decreases in switched memory B cells and classical monocytes in phototherapy-treated individuals. Since B cells are increasingly targeted by MS therapies, the effects of narrowband UVB phototherapy in people with MS should be investigated further.
Highlights
UV radiation (UVR) has a number of effects on local and systemic immunity
The current study investigated whether the frequencies of peripheral blood mononuclear cell (PBMC) subsets or serum immunoglobulins were altered by narrowband UVB phototherapy in the same cohort
Non-significant increases in FrIII cells were associated with phototherapy in the 1–2 months (2 M) model (Table 3, p = 0.07) and at 3 months (3 M) in linear regression models prior to adjusting for other variables (p = 0.09) but not after accounting for age, sex, and baseline 25(OH)D levels (p = 0.21) (Table 6)
Summary
Evidence from mouse studies shows that exposure to sub-erythemal UVR suppresses immune responses to topically applied experimental antigens that are taken up by Langerhans cells and dermal dendritic cells (DCs) and transferred to draining lymph nodes, inducing the generation of T-regulatory (Treg) cells. This process is assisted by UVR-induced immunoregulatory cytokines, neuropeptides and products of other pathways, including the vitamin D pathway, activated by UVR [reviewed in1,2]. These effects on PBMC populations were short-term, and one month after phototherapy was ceased, no significant effects of the intervention were detected
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