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  <xs:element id="lyel_DeferredTaxAssetsLeasingArrangements" abstract="false" name="DeferredTaxAssetsLeasingArrangements" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="lyel_LesseeOperatingLeaseNumberOfRenewalOptions" abstract="false" name="LesseeOperatingLeaseNumberOfRenewalOptions" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="lyel_TenTimesMember" abstract="true" name="TenTimesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="lyel_OperatingLossCarryforwardsSubjectToExpiration" abstract="false" name="OperatingLossCarryforwardsSubjectToExpiration" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="lyel_CollaborativeArrangementRightsAndObligationsAggregatePotentialSuccessPaymentsSharePrice" abstract="false" name="CollaborativeArrangementRightsAndObligationsAggregatePotentialSuccessPaymentsSharePrice" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types1:perShareItemType"/>
  <xs:element id="lyel_ExpiresInDecember2028Member" abstract="true" name="ExpiresInDecember2028Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="lyel_TemporaryEquityConversionOfConvertibleSecuritiesShares" abstract="false" name="TemporaryEquityConversionOfConvertibleSecuritiesShares" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="lyel_SonomaMember" abstract="true" name="SonomaMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="lyel_CowenAndCompanyLLCMember" abstract="true" name="CowenAndCompanyLLCMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="lyel_SaleOfStockMaximumConsiderationReceived" abstract="false" name="SaleOfStockMaximumConsiderationReceived" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="lyel_FredHutchSuccessPaymentLiabilityMember" abstract="true" name="FredHutchSuccessPaymentLiabilityMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="lyel_CollaborativeArrangementRightsAndObligationsSuccessPaymentExpenseGain" abstract="false" name="CollaborativeArrangementRightsAndObligationsSuccessPaymentExpenseGain" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="lyel_TwentyTimesMember" abstract="true" name="TwentyTimesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="lyel_SeriesAConvertiblePreferredStockMember" abstract="true" name="SeriesAConvertiblePreferredStockMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="lyel_CollaborativeArrangementRightsAndObligationsSuccessPaymentAgreementTriggerPeriodFromInitialPublicOfferingDate" abstract="false" name="CollaborativeArrangementRightsAndObligationsSuccessPaymentAgreementTriggerPeriodFromInitialPublicOfferingDate" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="lyel_CashPaidForAmountsIncludedInMeasurementOfLeaseLiabilities" abstract="false" name="CashPaidForAmountsIncludedInMeasurementOfLeaseLiabilities" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="lyel_CollaborativeArrangementRightsAndObligationsCommercialMilestonePayments" abstract="false" name="CollaborativeArrangementRightsAndObligationsCommercialMilestonePayments" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="lyel_AtTheMarketOfferingMember" abstract="true" name="AtTheMarketOfferingMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="lyel_CashEquivalentsAtCarryValueAndDebtSecuritiesAvailableForSaleAmortizedCost" abstract="false" name="CashEquivalentsAtCarryValueAndDebtSecuritiesAvailableForSaleAmortizedCost" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="lyel_TwoThousandEighteenEquityIncentivePlanMember" abstract="true" name="TwoThousandEighteenEquityIncentivePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="lyel_LesseeOperatingLeaseNumberOfContracts" abstract="false" name="LesseeOperatingLeaseNumberOfContracts" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="lyel_GSKMember" abstract="true" name="GSKMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="lyel_ShareBasedPaymentArrangementPlanModificationNumberOfSharesRepriced" abstract="false" name="ShareBasedPaymentArrangementPlanModificationNumberOfSharesRepriced" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="lyel_FortyTimesMember" abstract="true" name="FortyTimesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="lyel_FredHutchMember" abstract="true" name="FredHutchMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="lyel_StockPurchaseAgreementSharesSold" abstract="false" name="StockPurchaseAgreementSharesSold" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="lyel_CashEquivalentsAndDebtSecuritiesAvailableForSaleAbstract" abstract="true" name="CashEquivalentsAndDebtSecuritiesAvailableForSaleAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="lyel_ComputerEquipmentAndSoftwareMember" abstract="true" name="ComputerEquipmentAndSoftwareMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="lyel_OtherInvestmentMember" abstract="true" name="OtherInvestmentMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="lyel_AccruedPropertyAndEquipmentCurrent" abstract="false" name="AccruedPropertyAndEquipmentCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="lyel_LesseeOperatingLeasesArea" abstract="false" name="LesseeOperatingLeasesArea" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types1:areaItemType"/>
  <xs:element id="lyel_A2023Member" abstract="true" name="A2023Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="lyel_AdjustmentToRevenueRelatedToChangeInEstimateMember" abstract="true" name="AdjustmentToRevenueRelatedToChangeInEstimateMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="lyel_StockPurchaseAgreementFairValueOfStockPerShare" abstract="false" name="StockPurchaseAgreementFairValueOfStockPerShare" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types1:perShareItemType"/>
  <xs:element id="lyel_CollaborativeArrangementRightsAndObligationsAnnualLicenseMaintenancePayments" abstract="false" name="CollaborativeArrangementRightsAndObligationsAnnualLicenseMaintenancePayments" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="lyel_ShareBasedPaymentArrangementOptionAndRestrictedStockMember" abstract="true" name="ShareBasedPaymentArrangementOptionAndRestrictedStockMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="lyel_CollaborativeArrangementRightsAndObligationsSuccessPaymentAgreementTerm" abstract="false" name="CollaborativeArrangementRightsAndObligationsSuccessPaymentAgreementTerm" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="lyel_CollaborativeArrangementRightsAndObligationsAggregatePotentialSuccessPayments" abstract="false" name="CollaborativeArrangementRightsAndObligationsAggregatePotentialSuccessPayments" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="lyel_CollaborativeArrangementRightsAndObligationsSuccessPaymentAgreementLiability" abstract="false" name="CollaborativeArrangementRightsAndObligationsSuccessPaymentAgreementLiability" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="lyel_CollaborativeArrangementRightsAndObligationsPotentialPaymentMultiplier" abstract="false" name="CollaborativeArrangementRightsAndObligationsPotentialPaymentMultiplier" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:pureItemType"/>
  <xs:element id="lyel_FairValueAdjustmentOfSuccessPaymentLiabilities" abstract="false" name="FairValueAdjustmentOfSuccessPaymentLiabilities" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="lyel_TwoThousandTwentyOneEmployeeStockPurchasePlanMember" abstract="true" name="TwoThousandTwentyOneEmployeeStockPurchasePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="lyel_OperatingLeaseRightOfUseAssetIncreaseDecrease" abstract="false" name="OperatingLeaseRightOfUseAssetIncreaseDecrease" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="lyel_CashEquivalentsFairValueDisclosureAndDebtSecuritiesAvailableForSale" abstract="false" name="CashEquivalentsFairValueDisclosureAndDebtSecuritiesAvailableForSale" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="lyel_ExpiresInMay2030Member" abstract="true" name="ExpiresInMay2030Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="lyel_CashReceivedForAmountsRelatedToTenantImprovementAllowances" abstract="false" name="CashReceivedForAmountsRelatedToTenantImprovementAllowances" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="lyel_EquityWarrantInvestmentMember" abstract="true" name="EquityWarrantInvestmentMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="lyel_EquityMultipleDomain" abstract="true" name="EquityMultipleDomain" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="lyel_StanfordMember" abstract="true" name="StanfordMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="lyel_LesseeCurrentAndNonCurrentLiabilitiesTableTextBlock" abstract="false" name="LesseeCurrentAndNonCurrentLiabilitiesTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:textBlockItemType"/>
</xs:schema>
