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Antigen-presenting cells are capable of participating in the stimulation of T cells by antigen presentation. Antigen-presenting cells are considered essential for the induction and expansion of the immune reaction, because their interaction with antigen is the first step in immune induction. We have studied the distribution of class II-expressing cells in developing, healthy and carious human teeth to clarify when human pulp acquires an immunologic defense potential. Antigen-expressing cells were identified immunohistochemically with HLA-DR monoclonal antibodies (for dendritic cells) and CD68 monoclonal antibodies (for macrophages). In the pulp of unerupted developing teeth, HLA-DR-positive cells were distributed mainly in and around the odontoblast layer. A few CD68 positive cells were located more coronary around the blood vessels. In erupted teeth, HLA-DR-positive cells were located, for the most part just beneath the odontoblast layer. CD68 positive cells were also located coronary mainly around the blood vessels. Superficial caries lesions caused an aggregation of HLA-DR-positive cells and macrophages in the dental pulp corresponding to the lesion. Our results showed that human teeth are already equipped with an immunological defense potential prior to eruption. In the initial stage of caries infection, an immunoresponse mediated by class-II-expressing cells is initiated in human dental pulp. [ABSTRACT FROM AUTHOR]

Hamster enamel protein extracts were analyzed by RP-HPLC and the isolated fractions by SDS-and Western blotting using polyclonal antibodies against recombinant mouse amelogenin and anti-peptide antibodies against the mouse exon 4-encoded sequence. Total RNA was extracted from enamel organ epithelia and, using a 3′ rapid amplification of cDNA ends (3′ RACE) technique, the coding regions for three different amelogenin isoforms were cloned along with the 3′ non-coding region. DNA sequencing revealed that the hamster amelogenin isoforms are 180, 73 and 59 amino acids in length, respectively. The 59-residue amelogenin corresponds to the leucine-rich amelogenin protein (LRAP), the 73-residue amelogenin corresponds to LRAP with the inclusion of the exon 4-encoded sequence, while the 180-residue amelogenin is the most abundant amelogenin isoform. Edman degradation was performed on purified hamster amelogenin, which provided the amino acid sequence in the region encoded by the 5′ PCR amplification primer used in cloning. Therefore, the entire derived amino acid sequence of hamster amelogenin was revealed. The hamster amelogenin amino acid sequence was aligned with all its known homologues. Hamster differs from rat and mouse amelogenin at only three amino acid positions. Southern blot analysis using a panel of restriction enzymes gave the same pattern for hamster DNA obtained from males and females, suggesting that in hamster, as in mouse, amelogenin is expressed from a single gene located on the X chromosome. [ABSTRACT FROM AUTHOR]

Class II major histocompatibility complex (MHC) antigen-expressing cells are generally associated with the early phase of the immune response. We have studied the distribution of class II-expressing cells in developing, normal, and carious human teeth to clarify when human pulp acquires an immunologic defense potential and how this reacts to dental caries. Antigen-expressing cells were identified immunohistochemically by means of HLA-DR monoclonal antibody. In the pulp of unerupted developing teeth, numerous HLA-DR-positive cells were distributed mainly in and around the odontoblast layer. In erupted teeth, HLA-DR-positive cells were located, for the most part, just beneath the odontoblast layer, with slender cytoplasmic processes extending into the layer. Superficial caries lesions caused an aggregation of HLA-DR-positive cells in dental pulp corresponding to the lesion. In teeth with deeper caries lesions, this aggregation of cells expanded to include the odontoblast layer. Also noted were HLA-DR-positive cells lying along the pulp-dentin border, with cytoplasmic processes projecting deep into the dentinal tubules, where they co-localized with odontoblast processes. These findings suggest that: (1) human dental pulp is equipped with immunologic defense potential prior to eruption; (2) in the initial stage of caries infection, an immunoresponse mediated by class-II-expressing cells is initiated in human dental pulp; and (3) HLA-DR-positive cells trespass deep into dentinal tubules as the caries lesion advances. 1 [ABSTRACT FROM AUTHOR]