Smmnaiy. The tuiitara, Sphcnodon punctatum, has been shown to produce :mtil)odit!s t(» Salmonella adelaide fliiKt'llin. Tlie serum of immunized itnimals contained immnuoylobulins which pusst'ssed sedinientiUion coefficients of approx. 18S and 7S. The 18S iminiiiK)^luhiilin.s roscmliled tho yM immiinogloltiilins of otlier vertehrates in size and polypeptide chain stnictnrf. Thr 7S immunolobiilins were antijienically related to the lSS proteins and possessed li^ht chains resembling those of the latter on gel electrophore.sis in urea. Tbe heavy chains of the 7S protein dilfered from those of the macroglobnlin. thereby indicating the presence of distinct imniunoglubidin cla-Sfies. Although the immunization period lasted for over eight months, antibody activity was found only in the 18S imuiimoglobulin.The lymphoid system of the tuatara was found to be primitive. Tbe only clearly recognizable lymphoid organ in the adult animal was tbe spleen which showed a definite demarciihon into wbite pnlp and red pulp, Injected carbon particles were taken up only by tlie bver. The forHgii particles in this organ were associated with phagocytie cells whith resembled the Kuplfer-cells of the mammalian liver.The fact that this ancient reptile possessed multiple classes of immnnoglobulins is consistent with previous findings that distinct inunimoglobulin classes, defined by the presence of different heavy chaim. were present by the phylogenetic level of higher amphibians.
Summary Proteins resembling immunoglobulins of other vertebrate species in physical and chemical properties were instigated from the serum of unimmunized Australian lungfish (Neoceratodus forsteri). Two types of antigenically related proteins, characterized by sedimentation coefficients of 19.4S and 5.9S, were observed. Both proteins possessed light polypeptide chains which resembled typical immunoglobulin light chains in molecular weight (23,000) and behaviour in gel electrophoresis. The 19.4S proteins were similar to γM immunoglobulins of other vertebrates in size and chain structure. Heavy polypeptide chains from these molecules were comparable to the μ‐chain in molecular weight (70,000) and gel electrophoretic properties. The heavy chain of the 5.9S immunoglobulin‐like protein differed from those of the major classes of vertebrates in possessing a molecular weight of approximately 40,000. In both proteins the light chains and heavy chains were linked through disulfide bonds. These data suggest that lungfish resemble higher vertebrates in possessing different immunoglobulin classes defined by the presence of distinct heavy chains. The low molecular weight type of immunoglobulin‐like proteins may represent a class of immunoglobulins which is unique to Dipnoi.
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