Microarray analyses have contributed greatly to the rapid understanding of functional genomics through the identification of gene networks as well as gene discovery. To facilitate functional genomics of the inner ear, we have developed a mouse inner-earpertinent custom microarray chip (CMA-IE1). Nonredundant cDNA clones were obtained from two cDNA library resources: the RIKEN subtracted inner ear set and the NIH organ of Corti library. At least 2000 cDNAs unique to the inner ear were present on the chip. Comparisons were performed to examine the relative expression levels of these unique cDNAs within the organ of Corti, lateral wall, and spiral ganglion. Total RNA samples were obtained from the three cochlear-dissected fractions from adult CF-1 mice. The total RNA was linearly amplified, and a dendrimer-based system was utilized to enhance the hybridization signal. Differentially expressed genes were verified by comparison to known gene expression patterns in the cochlea or by correlation with genes and gene families deduced to be present in the three tissue types. Approximately 22Y25% of the genes on the array had significant levels of expression. A number of differentially expressed genes were detected in each tissue fraction. These included genes with known functional roles, hypothetical genes, and various unknown or uncharacterized genes. Four of the differentially expressed genes found in the organ of Corti are linked to deafness loci. None of these are hypothetical or unknown genes.

Burova, L. A., Koroleva, I. V., Ogurtzov, R. P., Murashov, S . V., Svensson, M-L. & Schalen, C. Role of streptococcal IgG Fc receptor in tissue deposition of IgG in rabbits immunized with Streptococcus pyogenes. APMIS 100: 567-574, 1992.Induction of anti-IgG during hyperimmunization of rabbit with Streptococcus pyogenes (group A streptococci; GAS) was previously shown to require the presence of IgG Fc receptors (FcR) in the vaccine strain. In the present work, we examined whether streptococcal FcR activity might also be of importance for heart and kidney deposition of IgG, known to occur in poststreptococcal sequelae as well as during experimental immunization of animals. Each of three IgG-binding (GAS types M1, M12 and M22) and two non-binding (GAS type T27 and S. agalactiae (GBS) type Ia) streptococcal strains were used for intravenous immunization of rabbits during two periods of eight and six weeks, respectively, separated by an interval of one month. Before use, vaccine strains were treated with KSCN and carefully washed in order to remove any surface-bound immunoglobulins. No deaths occurred among injected rabbits. No tissue deposition was elicited by the GAS type T27 or the GBS strain. In contrast, the strains of types M1, M12 and M22 all induced deposits of IgG in kidney and heart tissue, beginning during the first immunization period. In two tested animals, receiving GAS of types MI or M22, circulating immune complexes containing anti-IgG antibodies were also detected. Finally, serum autoantibodies reacting with preparations of heart and kidney, but not lung or liver, were demonstrated in each of six animals receiving M1 or M22, reaching maximum levels during reimmunization; such antibodies were not evoked by the two strains not binding IgG. Our results suggest that, in GAS with capacity for non-immune binding of IgG, triggering of anti-IgG acted to enhance tissue deposition of IgG or immune complexes in immunized rabbits. Furthermore tissuespecific antibodies were elicited only by the IgG-binding strains and occurred comparatively late during immunization, suggesting that those antibodies might have been triggered due to the exposition of hidden kidney and heart determinants.

No abstract

Binding of C1q, the first component of the complement system, to some human pathogens has been earlier reported. In the present study, direct binding of C1q to group A streptococci (GAS) of various serotypes as well as some other Gram‐positive and Gram‐negative species was demonstrated. The interaction between C1q and GAS was investigated more in detail. In hot neutral extracts of a number of GAS strains two components of 64 and 52 kDa, respectively, bound C1q; alkaline and SDS extracts yielded the 52 kDa component as the main C1q‐binding substance. Trypsin treatment of the SDS extracts of two GAS strains suggested the C1q‐binding component(s) to be of protein nature. C1q‐binding material purified from the SDS extract of an avirulent strain, type T27, was separated in 12% SDS‐PAGE and probed in Western blot with human C1q and fibrinogen, conjugated to horse radish peroxidase (HRP) as well as rabbit IgG antibodies complexed to HRP (PAP system). The 52 kDa component was non‐reactive with fibrinogen or rabbit IgG. However, C1q‐binding components purified from the alkaline extracts of two M‐positive strains revealed strong binding of either fibrinogen (type M5) or both fibrinogen and rabbit IgG (type M76); the molecular mass of these components, 55 kDa and 43–40 kDa, respectively, was in agreement with the reported molecular mass of the M5 and FcRA76 proteins. Our findings suggest that C1q may interact with GAS through certain M‐family proteins as well as by a so far unidentified surface factor of protein nature occurring in most GAS strains. The involvement of M‐family proteins, regarded as virulence factors of these organisms, may suggest the interaction of GAS with C1q as biologically important.

Previous work has demonstrated that streptococcal IgG Fc‐receptors (FcR) may trigger production of anti‐IgG after immunization of rabbits with group A streptococci. This effect seemed dependent on in vitro binding of IgG, derived from the growth medium, to the vaccine strains. In the experiments presented here, IgG was eluted from streptococcal strains to be used for immunization of rabbits by 1 M KSCN and washing, a treatment which did not affect the capacity of the strains to bind newly added IgG. Using two IgG FcR‐positive group A streptococcal strains (M‐types 1 and 22) for intravenous immunization, anti‐IgG was found in the sera of 26 out of 28 rabbits, examined 8 weeks after immunization. In contrast, anti‐IgG was not induced in 16 rabbits receiving either group A, type T27 or group B, type Ia streptococci both of which lack surface FcR activity. Finally, immunization with purified streptococcal IgG FcR (0.35 mg, given subcutaneously combined with Freund's complete adjuvant and two weeks later intraconjunctivally without adjuvant) also induced anti‐IgG. In all rabbits, anti‐human rather than anti‐rabbit IgG was detected. It is proposed that in vivo interaction between the bacterial FcR and rabbit IgG, resulting in conformation changes in IgG, is a prerequisite for the induction of anti‐IgG. Thus, streptococcal triggering of anti‐IgG, ascribable to IgG Fc‐receptor activity and not requiring presence of foreign IgG, has been demonstrated in the rabbit.