Recently, we showed that EAU scores are increased in IRBP-immunized animals and inoculated with recombinant wild-type M. leprae
Hsp65. Interestingly, this was associated with a higher expansion of CD4+IFN-γ
+ (Th1) and CD4+IL-17+ T cells (Th17), and with higher levels of IFN-γ
]. Moreover, Marengo and collaborators still demonstrated that WT Hsp65 inoculation accelerates death in mice which spontaneously develop the Systemic Lupus Erythematosus (SLE) [8
In the present work, we showed higher EAU scores in animals injected with K409A and Leader pep. However, animals injected with K409A pep did not develop the disease. Histopathological analysis showed that animals injected with K409A pep did not show lesions of retina when compared to controls, otherwise K409A and Leader pep presented retinal folds, vasculitis, and inflammatory infiltrating cells in the vitreous.
To evaluate the effect of K409
A, Leader pep, and K409
A pep in the periphery, it was evaluated the CD4+ T cells producing IFN-γ
in spleen and lymph nodes of mice induced to EAU. In this model, the increase in CD4+ IFN-γ
+ T-cell population in lymph nodes and spleens was associated with the increased scores observed in the K409
A, Leader pep, and control groups. Friedland
and collaborators demonstrated that the secretion of proinflammatory cytokines from monocytes activated by mycobacterial 65
kDa Hsp may be important in the host immune response and in the development of antigen-specific T-cell-mediated immunity [20
Th17 cells were recently described as crucial for the development of EAU [21
]; however, it was not observed differences in IL-17 levels by splenocytes at day 21 after-immunization between the experimental groups. Thus, we may assume that, at this phase, the Th17 cells are in the eye. On the other hand, different from that we observed in the present work, it was previously shown an expansion of CD4+
T cells in mice injected with rHsp65 [16
It is known that the immunosuppressive cytokine IL-10 regulates EAU susceptibility and may be a factor in genetic resistance to EAU [19
]; the results showed that spleen cells from animals injected with K409
A pep produced higher levels of IL-10. The increase of IL-10 levels can be associated with the absence of the disease, as IL-10 is a potent suppressive cytokine. Moreover, as we did not evaluate Tregs, it is also possible that higher levels of IL-10 observed in Leader pep mice group may be derived from this population such as Tr1 cells or IL-10 secreting Foxp3+
In 2006, our group showed that rGal-1 administration was able to decrease the disease in mice with EAU, and this fact was associated with increased levels of IL-10 and decreased levels of IFN-γ
]. A study with experimental arthritis showed that antibodies against the Hsp molecule suppress inflammation by inhibiting the proinflammatory effect of the Hsp on the innate immune system. The increase in IL-10 secretion in the inflammatory site can skew the local cytokine profile from an inflammatory to an anti-inflammatory response and thus explain the mechanism of protection against inflammation by these antibodies [27
The opposite effects of the K409
A protein and their correspondent peptide which covers the 352–371 residues, the K409
A pep, in EAU score were unexpected. In (NZB×NZW)F1
mice, which present the H-2d/z
alleles, the inoculation of the Leader pep and K409
A pep shows resembled effects to their respectively proteins in the survival time, showing a amplified effect [17
]. Here, in the EAU susceptible B10.RIII mice, the H-2r
allele can explain at least in part their divergent effect. We can speculate that an important participation of the genetic background and immunobiological factors occurs. EAU is a organ-specific disease mediated by T-cells commitment, and SLE is a systemic disease characterized mainly by humoral self-response. Furthermore, differences at the H-2 loci in B10.RIII and (NZB×NZW)F1
mice suggest different or selective antigen-binding core and presentation to the immune system. Also, we can consider that the short length of the K409
A pep facilitates its antigen processing of these cells, being more effective than the K409
A protein. Some theoretical experiments based on molecules interaction by structural modeling studies can clarify the MHC molecules peptide binding to better comprehend the in vivo
findings observed to the mutant forms.
is based on the linear equation y
: this theoretical model presupposes that in anautoimmune process, it must be considered the entropy production [▲] during the disease progression where the slope a is the intensity and degree of the process aggravation; ▲, although variable to each individual, is a constancy for everyone, increasing at all illness episode [i
]. It was formulated the principle that the immunological history of an individual is unique and irreversible
, being cumulative in an autoimmune process, staying progressively far from the physiological equilibrium [8
]; thus, as for other autoimmunities syndromes, the uveitis is not reversible in the sense that the original immune state before the beginning of the disease cannot be reacquired. The general physiological conditions could be disrupted by similar homologous proteins, such as the M. leprae
Hsp that, along the life time, proceeds performing a pathological role. At each new episode, the entropy production is higher, and the disease progression could only be controlled or delayed.
Autoimmune disease aggravation: Y: the individual state of an irreversible immune responsiveness; a: disease degree; ▲i: entropy production, where i represents the number of autoimmune episodes being a time-dependent discrete variable.
In conclusion, K409A and Leader pep were able to aggravate EAU development when administrated at the same time with the immunization. Moreover, mice injected with Leader pep presented high scores of the disease associated with increase percentage of CD4+IFN-γ+ T cells. However, K409A pep was able to inhibit the development of EAU, and this fact can be associated with an increase observed in IL-10 levels by spleen cells and with a decrease in the percentage of CD4+IFN-γ+ T cells. The results of this study would contribute significantly to understanding of the role of the Hsp molecules in the pathogenesis of ocular autoimmune diseases. They also support the concept that immune responses to Hsp have potential importance in exacerbating and perpetuating organ-restricted autoimmune diseases.