Identical twins discordant for type 1 diabetes show a different pattern of in vitro CD56+ cell activation.
BACKGROUND
Recent studies in animal models indicate a role for natural killer (NK) cells in the protection against type 1 diabetes. In humans, a reduction of NK cell numbers has been reported in identical twins discordant for type 1 diabetes, irrespective of whether they have the disease. Here we have tested whether the activation and expansion of human NK cells with lipopolysaccharide (LPS) reveals differences between these twins.


METHODS
Proportions of CD56(+) NK cells and T-cells and Va24Vb11(+) NK-T cells from diabetic and non-diabetic twins was assessed before and after activation using flow cytometry. NK receptor usage was monitored by PCR and flow cytometry.


RESULTS
The profile of the expressed Killer Cell immunoglobulin-like receptor (KIR) repertoire (using mRNA) in freshly isolated NK cells was identical in pairs of identical twins, despite marked variation among individual twins as well as controls. Basal numbers of CD56(+) and CD94(+) (CD3(-) and CD3(+)) cells and Valpha24(+)Vbeta11(+) NK-T cells were similarly strongly correlated between identical twins (p < 0.006 for all correlations). Following LPS stimulation, the pattern of KIR mRNA expression remained unaltered in twins and the proportion of NK cells and Valpha24(+)Vbeta11(+) NK-T cells remained correlated between pairs of twins. However, there was a significant reduction in the proportion of CD56(+) cells and CD94(+) cells (whether defined as CD3(-) or CD3(+)) responding to LPS in the diabetic compared to the non-diabetic twin (p = 0.031 and 0.025, respectively).


CONCLUSIONS
This reduction in NK cell expansion in response to LPS in patients with type 1 diabetes is consistent with a non-genetically determined alteration in the innate immune response either predisposing to or resulting from the disease.
Department of Immunology Imperial College London, Faculty of Medicine, Chelsea and Westminster Hospital, UK. m.goodier@imperial.ac.uk
Martin R
MR
Goodier
Niga
N
Nawroly
Huriya
H
Beyan
Mohammed
M
Hawa
R David G
RD
Leslie
Marco
M
Londei
D019002:CD56 Antigen / Q000276:immunology*; D018929:Cell Culture Techniques; D003922:Diabetes Mellitus, Type 1 / Q000276:immunology*; D004200:Diseases in Twins; D006801:Humans; D007694:Killer Cells, Natural / Q000187:drug effects / Q000276:immunology*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008213:Lymphocyte Activation; D020559:Monomeric GTP-Binding Proteins / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014430:Twins, Monozygotic
D019002:CD56 Antigen; D008070:Lipopolysaccharides; C490245:GEM protein, human; D020559:Monomeric GTP-Binding Proteins