Immunodermatologic research started in 1963 with the description of the lupus band test (LBT) in lesional skin of patients with systemic lupus erythematosus (SLE) or discoid LE (DLE) independently by Burnham et al. (Burnham et al. 1963) and Cor- mane (Cormane 1964). Two years later, in 1965, Braun-Falco and Vogell (Braun-Falco and Vogell 1965), studying the skin of patients with LE with histochemical tech- niques, had observed periodic acid-Schiff (PAS)-positive precipitates along the der- moepidermal junction (DEJ) and had suggested using the then innovative direct immunofluorescence microscopy technique to further analyze these precipitates.
Since then, much has been published about the clinical and diagnostic relevance of the LBT (Mutasim and Adams 2001), but the pathomechanism of the immunoglobu- lin deposition beneath the epidermis in lesional or uninvolved skin of patients with LE and the antigens involved are still largely unknown (Sticherling 2001). Immuno- fluorescence studies in LE have mostly been performed in the skin of patients with typical DLE or subacute cutaneous LE (SCLE) or in acute lupus lesions of patients with SLE; atypical or uncommon manifestations of CLE such as LE tumidus, chilblain lupus, and LE profundus have been only infrequently investigated or have proved negative in immunohistopathologic studies. Equally, the immunopathomechanisms underlying the often widespread cutaneous and mucosal vasculitic lesions observed in more severe cases of SLE or overlap syndromes are still poorly understood (Werth et al. 1997), although they are probably closer related to the pathogenesis of organ, e. g., kidney or central nervous system, lesions in SLE. This chapter, therefore, concen- trates on the immunopathology of classic CLE lesions seen in sun-exposed or pro- tected skin.
Immunofluorescence Techniques in Cutaneous Lupus Erythematosus
Direct immunofluorescence (DIF) is routinely performed according to methods first outlined in detail by Beutner et al. (Beutner et al. 1965). The technique detects deposits of the immunoglobulins IgG, IgA, and IgM as well as of the complement components C1q, C4, and C3 at the DEJ of biopsy specimens taken from lesional or unaffected skin of patients with LE. Results are most reliable in snap-frozen skin biopsy samples. The sensitivity of the method may slightly decrease when fresh tis- sue, immersed in a suitable transport medium such as Michel’s solution, is first mailed to a reference laboratory before being processed for DIF. Since the relative
Immunopathology
of Cutaneous Lupus Erythematosus
Michael Meurer
22
intensity of fluorescence may vary in different biopsy sites and to a great extent depends on the duration and past treatment of a lesion, a standardized protocol is needed to ensure an optimal outcome and comparability of results for diagnostic and research purposes. If possible, facial lesions should not be biopsied since chronically sun-exposed facial skin often shows false-positive DIF results. It is known that the frequency and intensity of a positive LBT result increases with the age of a lesion;
therefore, LE lesions should be older than 4 weeks before biopsy – a prerequisite often impossible to meet in SCLE or SLE – and should be left either untreated or spared from previous treatment (e. g., with topical corticosteroids) for longer than 3–4 weeks before biopsy (Dahl 1983).
DIF Findings in Cutaneous Lupus Erythematosus (Table 22.1) All classes of immunoglobulins, occasionally including IgE and IgD, as well as the complement components C3, C4, C1q, MAC, properdin, and deposits of fibrin can be detected in a positive LBT result (Sontheimer and Provost 1991). The immune deposits most frequently present are IgM, IgG, and C3, and sometimes IgA (Wojna- rowska et al. 1986).
Discoid Lupus Erythematosus
The frequency of immune deposits in DLE depends on the biopsy site, past treatment, and the duration of a lesion. In lesional skin, immune deposits are present in about 60%–95% of DLE biopsy sample. IgG and C3 are most frequently detected. The pat- tern of the immune deposits can be linear in a continuous thick or thin band (Fig. 22.1) or discontinuous with coarse or fine granular deposits (Fig. 22.2). In addi- tion to the deposits along the DEJ, cytoid bodies can be present in the papillary der- mis, with positive staining mostly for IgM and IgA. In nonlesional skin, the LBT result is usually negative in sun-protected areas, eg, in biopsy samples taken from the but- tock area of patients with DLE; a recent study, however, described deposits of C3 and IgM in uninvolved skin of some patients with DLE (Cardinali et al. 1999).
Subacute Cutaneous Lupus Erythematosus
The composition and pattern of immune deposits in lesional SCLE skin are similar to those seen in DLE (Meurer and Bieber 1987). The LBT in lesional skin is positive in 60%–100% of biopsy samples from SCLE lesions; the frequency may vary with the
Table 22.1. Direct immunofluorescence findings (IgG) in lupus erythematosus (LE) Disease Lesional LBT (%) Nonlesional, sun-protected LBT (%)
Chronic discoid LE 60–90 0
Subacute cutaneous LE 60–100 0
Systemic LE 90–100 50–90
LBT, lupus band test.
duration of the subacute inflammatory skin lesions and with the anatomic location (Kay and Tuffanelli 1969). Unique to SCLE is a granular fluorescence seen in some patients with SCLE in the cytoplasm and in the nuclei of basal keratinocytes. This flu- orescence pattern is thought to be caused by the binding of anti-Ro/SSA or anti- La/SSB antibodies to their respective cytoplasmic or nuclear antigens (Baleski et al.
1992). The LBT result in nonlesional sun-protected skin of patients with SCLE is neg- ative in most cases; positive results, particularly when IgG deposits are found, point to an overlap with SLE (Sontheimer and Provost 1997).
DIF Findings in Systemic Lupus Erythematosus (Table 22.1) The DIF findings in biopsy samples obtained from typical SLE lesions are similar to those seen in DLE or SCLE: IgG, IgM, IgA, and C3 are most frequently detected, but other complement components and fibrin may be also present. The intensity of the LBT result in lesional skin was shown to correlate with serum titers of anti-DNA anti- bodies and with disease activity (Sontheimer and Gilliam 1979). As in other forms of
Fig. 22.1. Linear, band- like deposits of IgM along the dermoepider- mal junction of a chronic discoid lupus erythematosus lesion
Fig. 22.2. Granular deposits of C3 along the dermoepidermal junc- tion of a chronic dis- coid lupus erythema- tosus lesion (a similar pattern is often seen in a false-positive lupus band test result in non- lupus erythematosus inflammatory diseases) (Table 22.2)
LE, the pattern of immune deposits along the DEJ may be bandlike, linear, or granular.
In lesional skin of patients with SLE and active disease before systemic immunosup- pressive treatment, the LBT result is positive in 90%–100% of biopsy specimens.A neg- ative DIF finding in lesional skin makes a diagnosis of SLE very unlikely. In affected skin from patients with SLE, immune deposits may also be detected in other areas besides the DEJ: cytoid bodies mostly containing IgM or IgA can be present in the papillary dermis; around superficial dermal blood vessels, precipitates of immuno- globulins and complement may be located as in immune complex vasculitis (Fig. 22.3).
These vasculitic changes are specific to SLE and are not seen in DLE or SCLE; they are associated with other systemic immune complex-mediated disease processes, with hypocomplementemia and a serious outcome prognosis (Sontheimer and Provost 1997). In nonlesional sun-protected skin of patients with SLE, the probability of a posi- tive LBT result is much higher than in other LE subtypes and has been reported with a frequency between 50% and 90% (Halberg et al. 1982). The predictive value of a positive LBT result for the diagnosis of SLE is most reliable when deposits of IgG are present along the DEJ in biopsy specimens from uninvolved skin (Dahl 1983).
Immunopathology of the Lupus Band
The exact mechanisms leading to immune deposits along the DEJ in LE are still unknown. Despite numerous experimental attempts, the characterization of putative antigen(s) or specific antibodies within the lupus band have remained largely unsuc- cessful (Schreiner and Wolff 1970). It is likely that immunoglobulins and complement factors reacting with slowly released nuclear and cytoplasmic cell components from apoptotic keratinocytes are involved in the formation of such deposits (Casciola- Rosen and Rosen 1997). The polyanionic nature of some nuclear antigens such as native DNA may further induce or support a nonspecific binding to immunoglobulin aggregates and complement proteins such as C3 (Meurer and Gigli 1978). It is of interest that in SCLE or mixed connective tissue disease associated with high-titered serum autoantibodies to the nuclear U1RNP and La/SSB antigens or to the cytoplas-
Fig. 22.3. Perivascular deposits of IgG around a dermal vessel in lesional skin (systemic lupus erythematosus)
mic Ro/SSA antigen, DIF reveals nuclear or intracytoplasmatic fluorescence rather than the typical bandlike immune deposits seen in DLE where no antinuclear anti- bodies can be detected in the serum.
Diagnostic Relevance of the Lupus Band Test
Before interpreting a positive DIF finding in a presumed case of LE, several reasons for false-positive or false-negative results must be taken into account and excluded.
Linear deposits or dust-like particles mostly containing IgM and/or C3 can be seen along the DEJ in a great variety of other inflammatory skin diseases – often in facial or chronically sun-exposed skin (Table 22.2). Continuous deposits of IgG, however, are usually not found in such cases and are conspicuous of true LE. In sun-protected nonlesional skin, DIF findings are always negative in biopsy specimens from patients with the diseases listed in Table 22.2. False-negative results can be obtained when fresh lesions or lesions from patients treated topically or systematically with corticos- teroids or immunosuppressants are biopsied (Dahl 1983).
There is common understanding that a positive predictive or confirmatory value of the LBT in lesional skin for the diagnosis of LE is lower than the negative predic- tive value since a negative DIF finding in lesional skin is rather uncommon, whereas a (false-)positive DIF finding can be found in many other inflammatory skin diseases (Table 22.2). In nonlesional skin, however, a positive LBT result has a far higher posi- tive predictive value than a negative one and clearly points to a diagnosis of LE, espe- cially when deposits of IgG are present. Otherwise, the LBT, in lesional and unin- volved skin, has only little value for the distinction between DLE, SCLE, and SLE. For this purpose, serologic tests with demonstration of subtype-specific antinuclear anti- bodies are much more sensitive and specific (Conrad et al. 2000).
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Table 22.2.Diseases with immune deposits along the dermoepidermal junction (false-positive lupus band test result)
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