PL Antigens Research Articles

Prevalence and clinical significance of antiphospholipid antibodies to noncardiolipin antigens in systemic lupus erythematosus.

The specificity and immunoglobulin isotype distribution of antiphospholipid (aPL) antibodies have been evaluated in 68 patients with systemic lupus erythematosus (SLE) by ELISA which employed a panel of 7 different PL antigens. A total of 49 patients (72%) were positive for aPL antibodies of different isotypes and directed to one or more PL epitopes. Prevalence of IgG anticardiolipin (aCL, 37%) was similar to that of the other negatively charged PLs phosphatidylserine (PS, 35%), phosphatidylinositol (PI, 35%), phosphatidylglycerol (PG, 35%) and phosphatidic acid (PA, 40%); prevalence reduced to 9-12% and 7-16% respectively for IgM and IgA isotypes to the same antigens. aPL antibodies to the zwitterionic PLs phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were also observed, though their prevalence was lower than that demonstrated for negatively charged PLs. Of the 36 SLE patients who were aCL negative (53%), 17 (25% of all patients and 47% of aCL-negative patients) were positive for aPL antibodies of different isotypes to one or more non-CL epitopes. During a mean follow-up period of 30 months, 10 patients had deep vein thrombosis (DVT) with a total of 21 events. By chi 2 test, a significant correlation was found between DVT and IgG aCL (p = 0.03) and between this event and the presence of lupus anticoagulant (LA) antibody (p = 0.04). However, stronger correlations were demonstrated between DVT and IgA aCL (p = 0.007), IgG anti-PS (p = 0.02), and IgA anti-PC, -PI and -PG (p = 0.02, 0.003 and 0.02, respectively), whereas no correlation was found between thrombotic events and aPL antibodies with PE and PA specificities.(ABSTRACT TRUNCATED AT 250 WORDS)

Generation of discriminatory PL against HLA-D antigens not detected by serology

A family was studied in which the father and the mother were both homozygous for the HLA-DR antigens. All children responded to the parents in MLC, even though each had a copy of the parental DR antigen, implying that they recognized a difference. When the father or the mother was sensitized in PLT against any child, all siblings could restimulate equally well. However, by sensitizing a family member with one copy of the DR phenotype against another family member with the alternate form of the phenotype, discriminatory PL could be produced. This may help define the subtypic specificities of PL antigens.

Typing an unrelated panel with PLT cells: association with DW clusters.

Primed LD typing (PLT) cells prepared in one Laboratory (Madison) were shipped in the frozen state and tested in Tübingen on a separate panel that had been typed with homozygous typing cells. Those PLT cells that had been grouped, on the basis of their reaction with test cells of the Madison panel, as defining an HLA PL antigen showed identical or nearly identical patterns of reactivity with the Tübingen panel. Clear association between certain PL antigens and DW clusters as defined with homozygous typing cells could be demonstrated. Of particular interest may be combinations of certain PLT reactions with D-locus-typed cells, where the primed cells do not react as expected from the target's HLA-D type.

Response of primed LD typing cells to homozygous typing cells.

At least two different methods using cellular responses have been described for defining the determinants of the HLA-D region: typing with HLA-D homozygous cells and primed LD typing. Primed LD typing cells were generated in one-haplotype-different combinations and grouped on the basis of two or more cells appearing to define the same HLA-D-region-determined PL antigen. Such cells were restimulated with homozygous typing cells for several of the presently known HLA DW clusters. A very strong correlation was noted: PLT cells defining the antigen PL1 were restimulated with homozygous typing cells for DW3, those PLT cells defining the antigen PL2 were restimulated by homozygous typing cells for DW2, and those defining PL5 were restimulated by homozygous typing cells for DW1.

Primed LD typing: reagent preparation and definition of the HLA-D-region antigens.

Primed LD typing cells were prepared against single HLA haplotypes within families and used to type a random panel of 48 individuals. PLT cells could be grouped on the basis of highly correlated responses with the panel test cells; the 21 different PLT cells could be used to define 6 different PL antigens. One of these, PL 3, was split by the responses of two of the 21 PLT cells which measured an antigen called PL 3.1.